Based on 3-year continuous observations, the runoff characteristics of Pinus armandii man made plant community are researched, and the results are listed as follows: The season distribution of precipitation in the area is uneven, the rainfall of wet season (from Jun. to Oct.) accounts for 80% of yearly gross, the precipitation is mainly brought by rainfall with more than 10mm, and most of the rainfall intensities are less than 5.0mm/h. Monthly change tendency of runoff is similar to precipitation, and the relativity is preferable. The single rainfall obviously affect surface runoff (R=0.91), the critical single rainfall yielding surface runoff is 22.3mm. The surface runoff and subsurface runoff respectively account for 0.58% and 99.42% of total runoff, and the forest has obvious function of protecting water resources.