A decompressing method, comprising: receiving (101, 301) a compressed data packet and decompressing (101, 302) a sequence number compression code of the compressed data packet; obtaining a new reference sequence number according to time of receiving the compressed data packet, a buffered reference sequence number, reference time, and a unit sequence number time interval when a sequence number of the data packet fails to be decompressed because of successive packet losses; and re-decompressing (103, 309) the sequence number compression code of the data packet according to the new reference sequence number to obtain the sequence number of the data packet; wherein, the buffered reference sequence number is a sequence number of a last successfully decompressed data packet and the reference time is time of receiving a compressed data packet, and the data packet is the last successfully decompressed data packet; characterized in that the obtaining a new reference sequence number according to time of receiving the compressed data packet, a buffered reference sequence number, reference time, and a unit sequence number time interval comprises: calculating a time difference between the time of receiving the compressed data packet and the reference time; calculating a sequence number increment according to the time difference and the unit sequence number time interval, wherein the sequence number increment is obtained by dividing the calculated time difference by the unit sequence number time interval; and calculating the new reference sequence number according to the buffered reference sequence number and the sequence number increment, wherein the new reference sequence number is obtained by adding the buffered reference sequence number to the sequence number increment. receiving (101, 301) a compressed data packet and decompressing (101, 302) a sequence number compression code of the compressed data packet; obtaining a new reference sequence number according to time of receiving the compressed data packet, a buffered reference sequence number, reference time, and a unit sequence number time interval when a sequence number of the data packet fails to be decompressed because of successive packet losses; and re-decompressing (103, 309) the sequence number compression code of the data packet according to the new reference sequence number to obtain the sequence number of the data packet; wherein, the buffered reference sequence number is a sequence number of a last successfully decompressed data packet and the reference time is time of receiving a compressed data packet, and the data packet is the last successfully decompressed data packet; characterized in that the obtaining a new reference sequence number according to time of receiving the compressed data packet, a buffered reference sequence number, reference time, and a unit sequence number time interval comprises: calculating a time difference between the time of receiving the compressed data packet and the reference time; calculating a sequence number increment according to the time difference and the unit sequence number time interval, wherein the sequence number increment is obtained by dividing the calculated time difference by the unit sequence number time interval; and calculating the new reference sequence number according to the buffered reference sequence number and the sequence number increment, wherein the new reference sequence number is obtained by adding the buffered reference sequence number to the sequence number increment. calculating a time difference between the time of receiving the compressed data packet and the reference time; calculating a sequence number increment according to the time difference and the unit sequence number time interval, wherein the sequence number increment is obtained by dividing the calculated time difference by the unit sequence number time interval; and calculating the new reference sequence number according to the buffered reference sequence number and the sequence number increment, wherein the new reference sequence number is obtained by adding the buffered reference sequence number to the sequence number increment.