This paper introduces an approach for ground moving targets detection and motion parameter estimation based on multi-channel SAR system which requires three consecutive operations as follows: array calibration, clutter rejection and motion parameter estimation. The analytical expressions of cross-track velocity, along-track velocity, cross-track acceleration and along-track acceleration are derived for multi-channel synthetic aperture radar (SAR) system. On this basis, these motion parameters can be well estimated. Before clutter rejection, array calibration is performed to provide precise parameter estimation latter. Radon transform is used to detect the range walk and correct it. Doppler ambiguity is mitigated by compensating the cross-track velocity estimation. Simulated and real measured data verify the effectiveness of proposed approach.