Abstract: Compared to airborne radar, the height of space-based radar is much higher. Therefore, the earth cannot be assumed as flat surface, and the earth rotation must be considered in space-based radar clutter simulation. In this paper, a simulation method of space-based radar clutter is proposed. This method can be used to emulate the iso-range clutter of space-based radar with arbitrary orbit. The earth sphere model and the effect of earth’s rotation are considered in this method, with the longitude and latitude of the iso-range clutter points can be calculated. First, the position of the clutter point in earth centered inertial ( ECI) is calculated through projection and transformation of coordinate. Second, clutter Doppler frequency is calculated with the consideration of earth rotation. Then, the amplitude of clutter is calculated with the parameters of radar system like transmit power, antenna pattern and system loss, et al. The iso-range clutter is obtained in the final. Computer simulation validates the effectiveness of this method.