Abstract: The paper relied on 3 different age of Pinus armandii plantation on Mopa Mountain in Yunnan and used the method of long-term observation to analyze the characteristics of canopy interception and runoff, and effects of rainfall, rainfall intensity, stand density, leaf area index and other factors on canopy interception and runoff. Results showed that the total rainfall was 877.2 mm from May to September in 2016 on the Mopa Mountain, and the maximum rainfall appeared in August. Mature forest had the strongest effects on forest canopy interception, and then the half-mature, young forest. Under the condition of different ages of P.armandii plantation, the runoff and runoff coefficient of each month in young forest was the largest, and then the half-mature forest, mature forest. Runoff, canopy interception and canopy interception rate were extremely significant correlated with the rainfall and rainfall intensity. The direct effects of rainfall intensity on runoff was the largest, and the indirect effects of rainfall on runoff was the most important. The rainfall intensity influenced the forest canopy interception and canopy interception rate through direct and indirect ways. Effects of rainfall, rainfall intensity, stand density, leaf area index, stand age on canopy interception were great and they were positive correlation. The correlation coefficient between the forest canopy interception and rainfall was the greatest. Rainfall and rainfall intensity were the main controlling factors of forest canopy interception, rainfall in stand and runoff.