In inertial navigation system/synthetic aperture radar (INS/SAR) integrated navigation system, the traditional SRA only provides the position and heading angle. In this paper, the SAR velocit measurement system is introduced to realize the compensation for INS velocity information. A mathematical model is established for the integrated navigation filtering. In the view of the long-time image matching and asynchronous information, INS increment information is used to correct errors of SAR navigation delay, unequal information interval, unaligned time interval between SAR measurement and INS filtering. After 1 500 s simulation, navigation information does not appear to diverge in this navigation system. When the aircraft is accelerating, climbing and turning, the absolute value of the position error is less than 36.8m, height error is less than 18.1 m, heading error is less than 5.3′, and velocity error is less than 0.5 m /s. The results of curve fitting methods are also analyzed and compared with the simulation results. The simulation results show that the algorithm can effectively improve the accuracy of the INS/SAR integrated navigation system, and provide reference for other integrated navigation system.