Abstract: The SAR/GMTI in wide-swath can be obtained by reconstructing virtual space samplings of MIMO-SAR into equivalent observation channels. Based on the properties of the configuration of wide- swath MIMO-SAR, the echo signal of moving target was firstly studied to reveal the distinctness with the echo signal of traditional SAR system. The effect of the echo signal of moving target in MIMO-SAR was also studied using paired echo principle (PEP). This analysis decomposed the echo signal into equivalent micro-motion phenomenon, which had a similar characteristic with micromotion target. Then, the expected time-frequency spectrum of MIMO -SAR in wide-swath was discussed in detail. Finally, numerical simulations give the validity of conclusions.