Abstract: Tree canopy interception rainfall capacity not only reflects the degree of tree canopy intercept rainfall features, but also it is used to compare interception capacity among different stands. By analyzing data of deodar cedar(Cedrus)canopy intercepting rainfall, a relationship between intercepting capacity and rainfall was established approximately. A half-experience formula was built according the concept of relative curve between watershed storage-water capacity and area in hydrology,and a method of determinating three parameters in formula was also introduced. The results were trust worthly through verification.