To promote the evaluation precision of millimeter wave transmission attenuation in the complex precipitation condition, representative size distribution parameters for five kinds of precipitations (stratiform rain, mixed stratiform and cumulonimbus rain, cumulonimbus rain, dry snow and wet snow) were obtained by analysis of precipitation characteristics in many areas. Combined with the shape, phase and dielectric model of the precipitation particles, the scattering characteristics of precipitation particle clusters at the millimeter waveband were calculated. The numerical simulation results show that the precipitation intensity is not the only factor that influence the millimeter wave propagation characteristics; the phase of particle, drop size distribution, incidence wave frequency and temperature have different effects on the millimeter wave propagation, The size distribution and number density are the main factors influencing the millimeter wave propagation attenuated by rain. The composition of ice and water are the main factors influencing the millimeter wave propagation attenuated by snow. The phase of precipitation particles also have strong effect on the millimeter wave propagation. There are distinct differences between the snow and rain. The temperature is the least factors. At precipitation attenuation model was established based on the drop size distribution and temperature is established.