Based on the normalized raindrops size distribution，dielectric model of raindrop and Mie scattering theory，the scattering characteristic of raindrop cluster in the microwave and millimeter domain are calculated，the effect of raindrop size distribution，rain-rate，incidence wave frequency and temperature on the microwave transmission are discussed. The results show that the scattering capabilities of raindrop clusters decrease in the order of JD，MP，Gamma and JD. The effect of rain-rate on microwave transmission is the strongest，the incidence wave frequency takes second place，and the temperature is the weakest. These results will be helpful to the evaluation of the effect of precipitation on microwave transmission and the improvement of the precipitation detection precision of millimeter radar and precipitation-measuring radar，etc.