Abstract: In this paper, a method that is used to simulate distributed targets raw data of spaceborne polarization SAR is given. Based on the backscattering polarization matrix, the algorithm of computing distributed target backscattering coefficients is discussed. Then the process of obtaining the raw data is particularly introduced. Through analyzing the image that come from the simulated data, the conclusion can be reached that the method of simulating the polarization raw data of Spaceborne SAR is right.