A method and system for processing session initiation protocol messages including receiving a session initiation protocol message by a front end, parsing the session initiation protocol message by the front end, grouping the token types and the token contents in the session initiation protocol message respectively, and setting up corresponding links between the token types and the token contents, wherein the session initiation protocol message, after parsing, is transformed to the session initiation protocol offload engine message with a session initiation protocol offload engine message header part, for storing message level information, a token type part, for storing token type information, wherein it comprises a plurality of fixed-length entries, and a token content part for storing token contents, wherein it comprises a plurality of variable-length entries, and processing the transformed session initiation protocol offload engine message at the server end.