Abstract: Alternate transmission and reception is an effective way to obtain a longer along-track baseline and additional independent phase centers to improve the performance of Ground Moving Target Indication (GMTI) in single-platform multi-channel SAR systems. A theoretic analysis of the signal model of moving targets in multi-channel SAR systems with alternate transmission and reception is made. And the necessary condition for the existence of the along-track baseline is indicated. Based on the signal model and the theoretical derivation, the design consideration of the modes of alternate transmission and reception is given. The comparison of GMTI performance with different antenna partitions and alternating strategies shows that an appropriate antenna partition and alternating strategy is important in improving the GMTI performance. The correctness of the conclusion is experimentally verified by the simulated and real SAR data.