There are several sub-transmission processes before matching-position parameters are transferred into combination-filter in INS/SAR integrated navigation system. In this paper these processes were studied, and the relations between them were analyzed, including the transmission of position information from ground matching centre to SAR phase centre, the transmission of position information from SAR phase centre to assistant INS centre, and the transmission of position information from assistant INS centre to master INS centre. Based on the analysis, a mathematical model of parameter-transfer was established. Modified inertial navigation parameters based on the model are reasonable, and results of transfer errors are rational, which prove the efficiency and flexibility of the model proposed.