Abstract: Geosynchronous Orbit Synthetic Aperture Radar (GEO SAR) has the advantages of short revisit and large coverage. Distributed GEO SAR combines multiple GEO SAR to form multiple phase centers simultaneously, which can reduce the synthetic aperture time and improve the signal-to-noise ratio. The ambiguity is an important indicator for the design of radar systems. The traditional method of ambiguity calculation is usually carried out in the range time domain and azimuth frequency domain. However, in distributed GEO SAR, full aperture imaging is usually not necessary for general resolution, so the azimuth signal bandwidth is lower than the instantaneous Doppler bandwidth of the scene, which makes the ambiguity calculation method in the azimuth frequency domain invalid. In addition, the bistatic configuration and the Earth’s spherical surface also bring difficulties to the determination of the ambiguity regions. In this paper, an approximate calculation method of bistatic GEO SAR ambiguity region position is proposed firstly taking the Earth’s spherical surface into consideration, and then the calculation steps of distributed GEO SAR ambiguity are given. A comparison between the traditional frequency domain method and the proposed time domain method is carried out in the simulation, and the ambiguities of monostaitc GEO SAR, bistatic GEO SAR and multistatic GEO SAR are analyzed in detail.