Abstract: Canopy structure and precipitation features,canopy rainfall redistribution during growth period of four major tree species of protection forests in Miyun watershed were studied using fixed square arrangement method.Results show that rain throughfall is linearly correlated to rainfall outside of stands,and the regression coefficient can be used to assess evaporation ability of water stored on canopy;The interceptions amount increased with rainfall amount,and the interception percentage decreased with it,dropping down quickly during initial rainfall period and then slowly and finally reaching the canopy-saturated state.The saturated interception percentage was estimated 24.38% to 38.42% by models;Simulated four stands of protection forests by interception model,the relative error between the estimation value of this model and the measured value is below 0.8.This model can forecast seasonal and long term rainfall interception of stands.