Abstract: To study the earth's rotation effect on the Doppler frequency of ground clutter for space-based radar,in this paper,by analyzing the relative velocity between the satellite radar and the point of ground,a detailed derivation of the formula about Doppler frequency is presented.The effect of earth's rotation depends only on the satellite orbit inclination and its latitude,and not on the location of the ground refrecting point for a given height.The crab magnitude scaling the Doppler magnitude of clutter approximates to 1 and the maximum of crab angle affecting the azimuth angle approximates to 4°.