A three dimensional (3D) imaging method which is a complex-valued generalized Radon transform (CGRT)-CLEAN algorithm for circular synthetic aperture radar (CSAR) is proposed in this chapter. Based on the analysis of CSAR echo model, the echo of a scatterer in the range-azimuth domain can be modeled as a single cycle sinusoid. Inspired by the generalized Radon transform, this chapter utilizes the CGRT to estimate for scatterers’ positions. Then, combining the CGRT with CLEAN technique, the parameters of a scatterer which include position information and reflection coefficient can be obtained. Thus, a 3D image of a target can also be reconstructed. The performances of the CGRT-CLEAN method have been verified by simulations, and the results confirm the effectiveness of the proposed algorithm for processing CSAR data.