Abstract:  For the problem of shift and defocusing in SAR moving target imaging, a motion compensation method based on phase retrieval principle and ISAR algorithm is proposed. Firstly, the sub-image is selected from formed SAR image, and the original data of the ISAR processing obtained by inversion mapping. Then, the Automatic time-windowing algorithm and the Image Contrast-based Autofocus (ICBA) algorithm are adopted to compensate the error phase. Finally, the phase retrieval algorithm is used to achieve accurate phase compensation. The method exploits the fuzzy image information obtained by the coarse compensation as the a priori condition of the phase retrieval algorithm, which improves the convergence of the algorithm. The simulation results demonstrate the validity of the proposed algorithm.