Abstract: For the InSAR radar system of bistatic spaceborne formation, a system framework integrating SAR and phase synchronization is proposed. Based on the bistatic time synchronization error, a bistatic spaceborne phase synchronization design method considering the time synchronization error, SAR and phase synchronization transmit and receive link delay is proposed. The slave satellite echo signal phase and interference phase after phase synchronization compensation are given, and two time-varying phase error power spectral densities are derived. Theoretical analysis and simulation experiments show that after phase synchronization compensation, the time synchronization error does not affect the phase synchronization accuracy, but only the target position of the slave satellite. The constant phase error of the slave satellite echo is large, but it does not affect the imaging. The constant phase error of the interference is a few thousandths of a degree, which has a negligible impact on the interferometric height accuracy. The time-varying phase error of the slave satellite echo and the interference is similar to that of the primary satellite.