Synthetic aperture radar (SAR) has its own special features different from conventional radar. It has high processing gain, so jamming to SAR is more difficult than that to conventional radar. Jamming to SAR finds its important usage in some military scene. In this paper, the basic principle of the SAR deceptive jamming and the model of the jamming signal are discussed, and the simulations are made. Finally, two criterions used to evaluate jamming effectiveness are provided. The jamming effectiveness is checked up used these criterions by computer simulation.