Abstract: In SAR systems, it is necessary to consider that the energy of moving target in clutter cannot be accumulated caused by the velocity, which will lead to defocusing. For this issue, a novel four-channel SAR moving target indication approach under clutter is proposed by combining the sum-difference 2D angle estimation in this paper. Firstly, the sum-difference space-time adaptive clutter suppression technique is utilized to suppress the clutter. However, due to the non-cooperative of moving targets, the energy is dispersed among different bins. Therefore, this paper employs a 2D sum-difference angle measurement to gain estimation of 2D angle. At the same time, combines clustering techniques to concentrate the energy of moving target onto the corresponding resolution grid. Hence, according to the estimation of 2D angle, the energy accumulation is completed, which provides a new idea for moving target indication. Finally, some experiments are implemented to validate the proposed target detection approach.