Abstract: Due to the ultra-long aperture time and large coverage characteristics of Geosynchronous Synthetic Aperture Radar (GEO SAR), the troposphere freezing model in the traditional Low Earth Orbit SAR (LEO SAR) imaging is assumed to fail in the GEO SAR, thus it should take the effects of the temporal variation troposphere on the GEO SAR imaging into account. In this paper, the phase error introduced by the troposphere was analyzed by using the ray tracing method. Concurrently, through the establishment of a GEO SAR signal model under the influence of temporal variation troposphere, it has probed into the GEO SAR two-dimensional image shift and image defocusing phenomena caused by the troposphere, as well as analyzed and summarized the boundary conditions of relevant effects. Finally, the imaging results of GEO SAR under the effect of troposphere were obtained based on simulation parameters.