To understand the features of SAR images comprehensively, the influence of moving targets on SAR imaging is studied. First, analysis is made to the influence of uniformly-accelerating and uniformly-turning targets on SAR imaging in azimuth direction. The expressions of the moving features are derived. Afterwards, the expression of the skewing in distance produced by Doppler shift is derived by dechirping. Theoretical analysis and simulation results show that the moving targets have great influence on azimuth image and small influence on distance image. The research results are useful for understanding the change of moving target's SAR images.