A phase synchronization method, comprising: determining pulse widths of first and second phase synchronization signals and starting time of transmission of the first and second phase synchronization signals, wherein the starting time is located between two successive moments when radar signals are transmitted; controlling a first spaceborne Synthetic Aperture Radar, SAR, to transmit the first phase synchronization signal to a second spaceborne SAR according to the pulse width and starting time of the first phase synchronization signal; controlling the second spaceborne SAR to transmit the second phase synchronization signal to the first spaceborne SAR according to the pulse width and starting time of the second phase synchronization signal; determining a compensation phase according to a peak phase of the second phase synchronization signal received by the first spaceborne SAR and a peak phase of the first phase synchronization signal received by the second spaceborne SAR; and performing phase synchronization compensation on the radar signals received by the first spaceborne SAR and/or the second spaceborne SAR according to the compensation phase, characterized in that, determining the pulse widths of the first and second phase synchronization signals comprises: acquiring a beam position data parameter of a Bi-satellite SAR system; determining first and second free durations in each of two adjacent Pulse Recurrence Times, PRTs, according to the beam position data parameter, wherein the first free duration is a free duration between ending time of transmission of the radar signals and starting time of a radar echo sampling window in the PRT, and the second free duration is a free duration between ending time of the radar echo sampling window and starting time of next PRT; and determining the pulse widths of the first phase synchronization signal and the second phase synchronization signal according to the first free durations, the second free durations and a preset signal to noise ratio of the phase synchronization signals. determining pulse widths of first and second phase synchronization signals and starting time of transmission of the first and second phase synchronization signals, wherein the starting time is located between two successive moments when radar signals are transmitted; controlling a first spaceborne Synthetic Aperture Radar, SAR, to transmit the first phase synchronization signal to a second spaceborne SAR according to the pulse width and starting time of the first phase synchronization signal; controlling the second spaceborne SAR to transmit the second phase synchronization signal to the first spaceborne SAR according to the pulse width and starting time of the second phase synchronization signal; determining a compensation phase according to a peak phase of the second phase synchronization signal received by the first spaceborne SAR and a peak phase of the first phase synchronization signal received by the second spaceborne SAR; and performing phase synchronization compensation on the radar signals received by the first spaceborne SAR and/or the second spaceborne SAR according to the compensation phase, characterized in that, determining the pulse widths of the first and second phase synchronization signals comprises: acquiring a beam position data parameter of a Bi-satellite SAR system; determining first and second free durations in each of two adjacent Pulse Recurrence Times, PRTs, according to the beam position data parameter, wherein the first free duration is a free duration between ending time of transmission of the radar signals and starting time of a radar echo sampling window in the PRT, and the second free duration is a free duration between ending time of the radar echo sampling window and starting time of next PRT; and determining the pulse widths of the first phase synchronization signal and the second phase synchronization signal according to the first free durations, the second free durations and a preset signal to noise ratio of the phase synchronization signals. acquiring a beam position data parameter of a Bi-satellite SAR system; determining first and second free durations in each of two adjacent Pulse Recurrence Times, PRTs, according to the beam position data parameter, wherein the first free duration is a free duration between ending time of transmission of the radar signals and starting time of a radar echo sampling window in the PRT, and the second free duration is a free duration between ending time of the radar echo sampling window and starting time of next PRT; and determining the pulse widths of the first phase synchronization signal and the second phase synchronization signal according to the first free durations, the second free durations and a preset signal to noise ratio of the phase synchronization signals.