Abstract:This article is based on forest trials. It shows that rainfall through forest canopy makes up 82.1—86.3% of rainfall out of forest, interception of canopy and stemflow 11.7—15.0%, 0.5—5.0% respectively in the northeast mountains and middle land of Guangxi. The rules of three kinds of rainfall in various forest, and its linear equations have been worked out. It provides a simple method for studying rainfall balance, substance circulation and water conservation in different forest ecosystems.