Abstract: A new method of jamming to SAR-GMTI is proposed, which is called motion modulated and step frequency shifting compound interference. The carrier frequency of the jamming signal varies in step between the pulses, increasing or decreasing. And at the same time, an additional motion phase modulation is appended. In this way, a regional shielding interference area in the SAR imaging is formed. Then the performance of the jamming was analyzed. A GMTI instance with three channels was introduced and the result was explained in the paper. There are two advantages of this method. First, the size and position of the sheltered area can be controlled by changing the interference parameters. And second, the interference signal is matched to the filters of radar in a certain extent both in range and azimuth. So it requires relatively smaller interference power. The simulation results verified that this method has a good effect on the SAR imaging and SAR-GMTI imaging.