Abstract: Nonuniform sample of SAR signal will add the noise into the signals, mix the spectrum of the echo signals with the spectrum of the noises, increase ambiguity of the signals, and depress the SAR imaging quality. In wide swath SAR systems, the multi-channel receivers are used in Azimuth for high resolution image, the nonuniform sampling will be meted. This paper carefully analyzes the spectrum ambiguity of the nonuniform sampling SAR signal and reconstructs unambiguous spectrum of the signal by periodic time offset spectrum reconstruction way; Based on the difference and correlation between the multi-channel signals and single channel signal, we have finished the multi-channel SAR imaging by CS algorithm, the simulation results prove the correctness of theoretic analysis.