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                                                                    Exhibit 12.1

                                  CERTIFICATION

I, Sterling Du, certify that:

        1.      I have reviewed this annual report on Form 20-F of O2Micro
                International Limited;

        2.      Based on my knowledge, this report does not contain any untrue
                statement of a material fact or omit to state a material fact
                necessary to make the statements made, in light of the
                circumstances under which such statements were made, not
                misleading with respect to the period covered by this report;

        3.      Based on my knowledge, the financial statements, and other
                financial information included in this report, fairly present in
                all material respects the financial condition, results of
                operations and cash flows of the company as of, and for, the
                periods presented in this report;

        4.      The company's other certifying officer and I are responsible for
                establishing and maintaining disclosure controls and procedures
                (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) for
                the company and have:

                a) Designed such disclosure controls and procedures, or caused
                such disclosure controls and procedures to be designed under our
                supervision, to ensure that material information relating to the
                company, including its consolidated subsidiaries, is made known
                to us by others within those entities, particularly during the
                period in which this report is being prepared;

                b) [Reserved];

                c) Evaluated the effectiveness of the company's disclosure
                controls and procedures and presented in this report our
                conclusions about the effectiveness of the disclosure controls
                and procedures, as of the end of the period covered by this
                report based on such evaluation; and

                d) Disclosed in this report any change in the company's internal
                control over financial reporting that occurred during the period
                covered by the annual report that has materially affected, or is
                reasonably likely to materially affect, the company's internal
                control over financial reporting; and

        5.      The company's other certifying officer and I have disclosed,
                based on our most recent evaluation of internal control over
                financial reporting, to the company's auditors and the audit
                committee of the company's board of directors (or persons
                performing the equivalent functions):

                a) All significant deficiencies and material weaknesses in the
                design or operation of internal control over financial reporting
                which are reasonably likely to adversely affect the company's
                ability to record, process, summarize and report financial
                information; and

                b) Any fraud, whether or not material, that involves management
                or other employees who have a significant role in the company's
                internal control over financial reporting.

Date: June 20, 2005
                                       By:          /s/ STERLING DU
                                          --------------------------------------
                                                      Sterling Du
                                           President and Chief Executive Officer