In this paper, we present a shading jamming method for the Synthetic Aperture Radar and Ground Moving Target Indicator (SAR-GMTI). This method begins with intermittently sampling intercepted SAR signals, performing motion modulation, and then transmitting them. The motion modulation of SAR signals can produce a motion modulation effect and intermittent sampling repeater jamming can produce multi-fronted and lagged false targets along a range. Their combination provides a jamming effect of smart shading areas, which can’t be cancelled after multi-channel cancelling. The uniqueness of this jamming method is that the energy only appears on the moving target to be covered, so less jamming energy is needed. We analyzed the proposed jamming principle against GMTI using the tri-channel interference cancelling technique. Our simulation results verify our analyses and confirm its jamming effectiveness for SAR-GMTI.