Abstract: Multi-channel wideband radar requires not only the ability of high-resolution imaging for wide coverage, but also the ability of moving target detection. This paper proposes a method based on three-channel Terrain Observation by Progressive scan SAR (TOPSAR) mode for Ground Moving Target Indication (GMTI). First of all, the geometric model of the three-channel TOPSAR-GMTI system is established, and then full-aperture imaging method is used for processing the three-channel echo data. After that, the Displaced Phase Center Antenna (DPCA) and Constant False Alarm Rate (CFAR) methods are used to accomplish the detection of moving targets. Finally, the relationship between the interferometric phase and speed is deduced for seeking to estimate the speed of the target and remark its correct position in the SAR image. The results of simulation are provided to demonstrate the effectiveness of the proposed method.