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Exhibit 10.70

SECOND LOAN MODIFICATION AGREEMENT

        This Second Loan Modification Agreement (this "Loan Modification
Agreement') is entered into as of September 10, 2004, by and among (i) SILICON
VALLEY BANK, a California chartered bank, with its principal place of business
at 3003 Tasman Drive, Santa Clara, California 95054 and with a loan production
office located at One Newton Executive Park, Suite 200, 2221 Washington Street,
Newton, Massachusetts 02462, doing business under the name "Silicon Valley East"
("Bank") and (ii) ASPEN TECHNOLOGY, INC., a Delaware corporation with offices at
Ten Canal Park, Cambridge, Massachusetts 02141 and ASPENTECH, INC., a Texas
corporation with offices at Ten Canal Park, Cambridge, Massachusetts 02141
(jointly and severally, individually and collectively, "Borrower")

1.DESCRIPTION OF EXISTING INDEBTEDNESS AND OBLIGATIONS. Among other indebtedness
and obligations which may be owing by Borrower to Bank, Borrower is indebted to
Bank pursuant to a loan arrangement dated as of January 30, 2003, evidenced by,
among other documents, a certain Loan and Security Agreement dated as of
January 30, 2003 between Borrower and Bank, as amended by a certain letter
agreement dated February 14, 2003 and a certain First Loan Modification
Agreement dated June 27, 2003 (as amended, the "Loan Agreement"). Capitalized
terms used but not otherwise defined herein shall have the same meaning as in
the Loan Agreement.

2.DESCRIPTION OF COLLATERAL. Repayment of the Obligations is secured by the
Collateral as described in the Loan Agreement (together with any other
collateral security granted to Bank, the "Security Documents").

        Hereinafter, the Security Documents, together with all other documents
evidencing or securing the Obligations shall be referred to as the "Existing
Loan Documents".

3.DESCRIPTION OF CHANGE IN TERMS.

Modifications to Loan Agreement.

(i)The Loan Agreement shall be amended by deleting the following text appearing
in the definition of "Eligible Receivables" set forth in Section 8 of the Loan
Agreement:

"(ii) the Receivable must not be due under a fulfillment or requirements
contract with the Account Debtor or represent Deferred Revenue (provided,
however, Deferred Revenue offsets will not be deemed ineligible (if otherwise
eligible hereunder) as long as Borrower maintains, at all times, an Adjusted
Quick Ratio of at least 1.25 to 1.0),"

and inserting in lieu thereof the following:

"(ii) the Receivable must not be due under a fulfillment or requirements
contract with the Account Debtor or represent Deferred Revenue (provided,
however, Deferred Revenue offsets will not be deemed ineligible (if otherwise
eligible hereunder) as long as Borrower maintains, at all times, unrestricted
cash and/or cash equivalents at Silicon of at least $50,000,000.00),"

(ii)The Loan Agreement shall be amended by deleting the following text appearing
in Section 1 of the Schedule thereto.

"Letter of Credit/FX Contract/Cash Management Services Sublimit

(Section 1.5, 1.6, 1.7): $11,000,000 (of which only $10,000,000 may be used for
FX Reserve, less any amounts used for FX Reserve pursuant to, and as defined in,
the Exim Agreement)"

and inserting in lieu thereof the following:

"Letter of Credit/FX Contract/Cash Management Services Sublimit

(Section 1.5, 1.6, 1.7): $15,000,000.00"

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(iii)The Loan Agreement shall be amended by deleting Section 5(a)(i) and (ii) of
the Schedule thereto in their entirety and inserting in lieu thereof the
following:

"a. Minimum Tangible Net Worth:

Borrower shall maintain, as of the last day of each month, to be tested monthly,
a Tangible Net Worth of not less than the sum of (i) plus (ii) below:

(i)

(a)from August 1, 2004 through and including August 31, 2004—$116,000,000

(b)from September 1, 2004 through and including September 30, 2004—$140,000,000

(c)from October 1, 2004 through and including October 31, 2004—$128,000,000

(d)from November 1, 2004 through and including November 30, 2004—$116,000,000

(e)from December 1, 2004 through and including December 31, 2004—$140,000,000

(f) from January 1, 2005 and thereafter—$128,000,000; provided, however, the
Tangible Net Worth requirements set forth in subsections (a) through (f) shall
be reduced by the lesser of (x) the total restructuring charge incurred by
Borrower in its first fiscal quarter of 2005, or (y) $14,000,000.

(ii) 75% of all consideration received after August 1, 2004 from proceeds from
the issuance of any equity securities of the Borrower (other than (i) the
issuance of stock options, restricted stock or other stock-based awards under
the Borrower's director or employee stock incentive plans, or (ii) stock
purchases under the Borrower's employee stock purchase plan) and/or subordinated
debt incurred by the Borrower (net of refinanced amounts of existing
subordinated debt)."

(iv)The Loan Agreement shall be amended by deleting the following text appearing
in Section 5 of the Schedule thereto:

"Adjusted Quick Ratio" is the ratio of (i) Quick Assets to (ii) Current
Liabilities plus the face amount of all issued Letters of Credit (both hereunder
and under the Exim Agreement), less the current portion of Deferred Revenue and
other income received in advance."

and inserting in lieu thereof the following:

"Adjusted Quick Ratio" is the ratio of (i) Quick Assets to (ii) Current
Liabilities plus the face amount of all issued Letters of Credit (both hereunder
and under the Exim Agreement), less the current portion of Deferred Revenue and
other income received in advance, less the outstanding principal balance of all
debt subordinated to the Obligations on terms satisfactory to Silicon."

(v)The Loan Agreement shall be amended by deleting the following text appearing
in Section 5(c) of the Schedule thereto:

"c. Adjusted Quick Ratio:

Borrower shall maintain, at all times, to be tested quarterly, an Adjusted Quick
Ratio of at least 1.0 to 1.0"

and inserting in lieu thereof the following:

"c. Adjusted Quick Ratio:

Borrower shall maintain, at all times, to be tested monthly, an Adjusted Quick
Ratio of at least (a) 1.25 to 1.00 as of the last day of each January, February,
April, May, July, August, October and November during the term of this
Agreement, and (b) 1.50 to 1.00 as of the last day of each March, June,
September and December during the term of this Agreement."

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4.FEES. Borrower shall reimburse Bank for all legal fees and expenses incurred
in connection with this amendment to the Existing Loan Documents.

5.WAIVER. Bank hereby waives Borrower's failure to comply with the Minimum
Tangible Net Worth requirement set forth in Section 5(a) of the Schedule to the
Loan Agreement as of June 30, 2004 and July 31, 2004. The Bank's waiver of
Borrower's compliance with said foregoing affirmative covenant shall apply only
to the foregoing specific periods.

6.RATIFICATION OF NEGATIVE PLEDGE. Borrower hereby ratifies, confirms and
reaffirms, all and singular, the terms and conditions of a certain Negative
Pledge Agreements each dated as of January 30, 2003 between Borrower and Bank,
and acknowledges, confirms and agrees that said Negative Pledge Agreement shall
remain in full force and effect.

7.RATIFICATION OF PERFECTION CERTIFICATE Borrower hereby ratifies, confirms and
reaffirms, all and singular, the terms and disclosures contained in certain
Perfection Certificates each dated as of January 30, 2003 and acknowledges,
confirms and agrees the disclosures and information therein has not changed as
of the date hereof, except as set forth on Schedule 1 annexed hereto.

8.CONSISTENT CHANGES. The Existing Loan Documents are hereby amended wherever
necessary to reflect the changes described above.

9.RATIFICATION OF LOAN DOCUMENTS. Borrower hereby ratifies, confirms, and
reaffirms all terms and conditions of all security or other collateral granted
to the Bank, and confirms that the indebtedness secured thereby includes,
without limitation, the Obligations.

10.NO DEFENSES OF BORROWER. Borrower hereby acknowledges and agrees that
Borrower has no offsets, defenses, claims, or counterclaims against Bank with
respect to the Obligations, or otherwise, and that if Borrower now has, or ever
did have, any offsets, defenses, claims, or counterclaims against Bank, whether
known or unknown, at law or in equity, all of them are hereby expressly WAIVED
and Borrower hereby RELEASES Bank from any liability thereunder.

11.CONTINUING VALIDITY. Borrower understands and agrees that in modifying the
existing Obligations, Bank is relying upon Borrower's representations,
warranties, and agreements, as set forth in the Existing Loan Documents. Except
as expressly modified pursuant to this Loan Modification Agreement, the terms of
the Existing Loan Documents remain unchanged and in full force and effect.
Bank's agreement to modifications to the existing Obligations pursuant to this
Loan Modification Agreement in no way shall obligate Bank to make any future
modifications to the Obligations. Nothing in this Loan Modification Agreement
shall constitute a satisfaction of the Obligations. It is the intention of Bank
and Borrower to retain as liable parties all makers of Existing Loan Documents,
unless the party is expressly released by Bank in writing.

12.COUNTERSIGNATURE. This Loan Modification Agreement shall become effective
only when it shall have been executed by Borrower and Bank.

[Remainder of page intentionally left blank.]

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        This Loan Modification Agreement is executed as a sealed instrument
under the laws of the Commonwealth of Massachusetts as of the date first written
above.

 

BORROWER:
 
ASPEN TECHNOLOGY, INC.
 
By:          
Name:                      
Title:            
 
ASPENTECH, INC.
 
By:          
Name:                      
Title:            
 
BANK:
 
SILICON VALLEY BANK, d/b/a
SILICON VALLEY EAST
 
By:          
Name:                      
Title:            

        The undersigned, ASPENTECH SECURITIES CORP., a Massachusetts
corporation, ratifies, confirms and reaffirms, all and singular, the terms and
conditions of a certain Unlimited Guaranty dated January 30, 2003 (the
"Guaranty") and a certain Security Agreement dated as of January 30, 2003 (the
"Security Agreement") and acknowledges, confirms and agrees that the Guaranty
and Security Agreement shall remain in full force and effect and shall in no way
be limited by the execution of this Loan Modification Agreement, or any other
documents, instruments and/or agreements executed and/or delivered in connection
herewith.

ASPENTECH SECURITIES CORP
  By:          
Name:                      
Title:              

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Exhibit 10.70