We describe the response of synthetic aperture radar to precipitation normalized radar cross section using a forward scattering model. Based on the snow-layer, rainfall-layer, and zero-layer bright band, the attenuation models of volume scattering and surface scattering echoes are established, and a retrieval algorithm based on a three-layer structure is proposed. The information of the starting point and width of the rainfall area is obtained by data preanalysis, and then the precipitation intensity is inverted by combining the model-oriented statistical and Volterra integral equation methods. The retrieve results in three cases show that the algorithm is scientific and effective, reduces the hypothetical conditions of the model, reduces the error of retrieve of precipitation by bright band, and the retrieved data are accurate and reliable.