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Multiple-input multiple-output SAR (MIMO-SAR) can transmit multiple waveforms and separate the radar echoes, which enables it to work in several modes simultaneously such as spotlight, sliding spotlight and strip-map modes. However, most of the existing waveforms are not well orthogonal, which cannot separate the echo completely and thus degrade the performance of MIMO-SAR applications. To solve this problem, a novel digital beam-forming (DBF) method for multi-modes MIMO-SAR based on APC waveforms is proposed in this paper. Due to the Doppler shift effect of the APC waveforms, the spectrum of overlapped echoes change with azimuth angles. Therefore, the digital beam-forming (DBF) in azimuth can be used to separate the echoes well. Finally, simulations of both point target and distributed target are conducted to validate the effectiveness of the proposed method.