The effects of platform rotation in three directions, yaw, pitch and roll, on synthetic aperture radar(SAR) imaging were analyzed. The platform rotation model was built , the analyses were conducted into three aspects: the change of the radar radiation area, the amplitude modulation and the phase modulation of the echo, and the effects of platform rotation on the imaging width and azimuth focusing were analyzed quantitatively.Simulation results show that platform rotation reduces the imaging width and leads to azimuth defocusing, so as to change the target azimuth position, which can provide guidelines for SAR system design and algorithm development.