Synthetic Aperture Radar (SAR) is an all-day, all-weather high-resolution senor that has been widely used in civilian mapping, military investigation, and strategic reconnaissance. Ground Moving Target Indication (GMTI) can detect and track moving targets, and obtain their moving information, which has been an important application of SAR for ground moving target detection and imagery. SAR, which has GMTI capability, can obtain focused stationary target images and moving target information at the same time, and form a more detailed battlefield map. Thus, it has increasingly become an important part of battlefield surveillance and strategic reconnaissance systems. Jamming technology research against SAR-GMTI has been an issue in the area of electronic countermeasures because of the growing threat of SAR-GMTI systems to important military moving targets. SAR-GMTI systems typically use multiple channels to suppress cluttering and jamming. Thus, traditional jamming methods for SAR are usually invalid for SAR-GMTI systems. In this paper, a new jamming method for multi-channel SAR-GMTI is proposed; this method is cosinusoidal phase-modulated repeater jamming based on a moving jamming station. First, the imaging feature of repeater jamming of a moving jamming station is analyzed by the principle of stationary phase and is used to realize azimuth jamming extension. At the same time, the cosinusoidal phase-modulated signal model is proposed and used to realize range jamming extension, thereby enabling their combination to realize two dimension jamming extension in range and azimuth. Second, the jamming performance of the proposed method for SAR is analyzed thoroughly, and the relationship between jamming parameters and performance is obtained. Then, the countering performance against SAR-GMTI is analyzed by using the cancelling technique of tri-channel interference,and the cancelling output expression of the final interference is derived. Finally, the simulation experiment and application example are presented. Computer simulation and theoretical analysis show that the method can produce flexible and controlled two dimension banded or planar-covering jamming performance for SAR and SAR-GMTI. Moreover, because of interference suppression and cancellation of multi-channel GMTI, the amplitude of false targets is affected by sinusoidal modulation coefficient, thereby revealing enhanced and weakened areas. The proposed method is simple, flexible, and controllable. Compared with the deceptive jamming method, its dependence on reconnaissance is lower; and compared with the traditional barrage jamming method, its jamming signal power requirement is lower because of the high two dimension coherent processing gain. The method can protect stationary and moving ground targets at the same time, thereby effectively strengthening the countering performance for multi-channel SAR-GMTI systems. Moreover, the method has important military application value.