Abstract: Firstly, electromagnetic scattering model of precipitation particle is analyzed. In order to research the scattering from raindrop particle in the Ku-band and Ka-band, the fast and accurate transfer matrix method (T-matrix) is used to analyze simple spherical or ellipsoid targets. Secondly, the influence of rainfall attenuation in multi-band and different rain rate is investigated. Finally, an imaging simulation method of 3-D complex target in rainfall environment is proposed. Simulation results demonstrate the influence of precipitation attenuation must be considered in Ku-band, while the rainfall intensity is above 10 mm/h. And SAR images in Ku-band will appear a much more severe degradation, when the rain rate increases to 50 mm/h. In Ka band, it is obvious that even impact of light rain could be seen in the images. And medium or heavy intensity precipitation will make SAR images nearly or completely blurred.