The azimuth multichannel SAR, which is based on multichannel sampling and azimuth spectrum reconstruction, breaks through the ambiguity design constraints, and has the capability of wide swath and high resolution at the same time. However, the amplitude and phase inconsistency of the multichannel and the instability of the satellite attitude cause the error, which results in the decrease of the SAR imaging quality. In this paper, the effect of channel error on the quality of azimuth multichannel SAR imaging is studied. Firstly, the multichannel SAR signal model with channel error is analyzed; the channel error compensation process and spectrum reconstruction method are presented; According to the signal error model and spectral reconstruction algorithm is given with simulation data, the influence of different channel errors on the performance of SAR is analyzed in detail, and the results are used to guide the design of multichannel SAR system.