When high power microwave is propagating in Rain, Elcctrommagnctic wave will be induced attenuation and depolarization for absorbency and dispersion of nonspherical raindrops, with the hoist of frequency, the attenuation and depolarization will become worse and worse . In the paper CPA of rainfall in correlation area based on factual metrical rainfall condition is advanced reckoned, and inclination angle of raindrops is considered, which amend old formula for calculating XPD, finally produce the model of microwave propagation which can avoid the effect of rainfall depolarization.