Because of go-stop mode not applying to FMCW CSAR (frequency modulated continuous wave circular synthetic aperture radar), received signal include Doppler shifting result from the radar fly in one period, which have a bad effect on the quality of imaging in wide-field FMCW CSAR. However the compensation functions of liner SAR are not suitable for CSAR. To solve the problem, the paper rebuild a received mode and elicit the Doppler shifting. At the same time, based on the model, the paper analysis the layover phenomenon while obtaining two-dimensional (2D) representations of 3D large scenes due to the wide-field FMCW CSAR and simulate the phenomenon. By the simulation, the effect of the layover can be expressed clearly.