Abstract: Geosynchronous spaceborne-airborne bistatic synthetic aperture radar （GEO SA-BSAR） system has a GEO transmitter， and the aircraft is equipped with multi-channel antennas to receive signals. GEO can provide a long-term stable beam coverage， which is convenience for moving target detection and monitoring. However， the GEO SA-BSAR system uses different frequency source between transmitter and receiver， leading to a time synchronization error and the performance degradation of the moving target indication （MTI）. In order to study the impact of time synchronization error on MTI performance in GEO SA-BSAR system， the multi-channel moving target signal under the influence of time synchronization error is modeled in this paper， and the relationship between MTI performance indicators and time synchronization error is deduced. The theoretical analysis and simulation results show that the time synchronization error will lead to the output SNR loss and the radial velocity estimation error of the target.