Precipitation redistribution is one of the most important effect of canopy interception, which caused the large variations of the quantity and spatial distribution of throughfall rain. This hinders both the accurate assessment of interception and is often considered to be one of the uncertain sources of evaporation quantification in hydrological models. A total of 37 gauges (cross-sectional area of 314.15 cm²) were mechanically arranged within a 30 m×30 m sample plot of Cryptomeria japonica stands in Mount Lu national natural reserve. During the 2017 growing season (April-September), a total of 21 rainfall events were monitored for rainfall. The results showed that the range of throughfall percentage varied between 2% and 222%, and the mean value was 80%. When the rainfall reaches 28 mm, the penetration rain rate tends to the maximum, and then the change law is complicated and not stable. The best fitting relationship between rainfall and throughfall could be described with a quadratic polynomial. Penetrating rain rate was significantly negatively correlated with the leaf area index. When the leaf area index was less than 4.5, the impact on the penetration rain rate was significant. Under different leaf area indexes, the rainfall outside the forest is different when the penetration rain rate reaches the maximum. The spatial variation coefficient of the penetration rain rate varies from 15% to 114%, which decreases with the increase of the rainfall outside the forest, and gradually stabilizes after the secondary rainfall outside the forest is greater than 20 mm. Logarithmic function relationship fitting. The coefficient of time variation of the observation points increases with the increase of the leaf area index.