Abstract: Multi-channel SAR in azimuth, which can be used to suppress the Doppler ambiguity to get the High-Resolution Wide-Swath (HRWS) SAR images, suffers from the amplitude and phase mismatch among the channels, as well as the position measurement inaccuracy of the antenna phase centers. Based on the analysis of the phase error characteristics of the multi-channel SAR, this paper presents a novel data-based phase error estimation method in time-domain. Firstly, the echoes in time-domain received by the adjacent channels are processed to get interferometric phases, which consist of the Doppler centroid information and the difference of the phase biases between the adjacent channels. The Doppler centroid can be extracted by circular integral of the adjacent interferometric phases. Finally, the phase bias between each channel and the reference one can be obtained by integral of the interferometric phase subtracted by the phase of the Doppler centroid. Using the presented method, both the phase bias and the Doppler centroid of the raw echoes can be effectively estimated. The performance of presented method is validated by the experiments of simulated spaceborne multi-channel SAR data.