So far, INS/satellite integrated navigation systems have been applied widely in aviation, aircraft automatic approach and landing, land vehicle navigation and tracking, marine applications, and surveying, etc., due to their complementary characteristics. Before the data fusion, the synchronization of data from various systems is the vital challenge and significant guarantee of the integrated navigation system performance. A novel synchronization approach is presented that models the asynchronous time between INS and satellite system data and then estimates it on-line by the Kalman filter in the process of integration. Compared with other synchronization methods, this approach is simple but practical, without any increasing load of the system hardware. And simulation results indicate that the asynchronous time can be estimated real time and the estimated error is smaller than 0.1s. Meanwhile, the accuracy of the integrated navigation system is enhanced remarkably. On the ground of simulation results, it is demonstrated that the synchronization approach proposed in this article is effective.