Abstract: According to the 3 years' observation on the precipitation and runoff in Pinus armandii forest watershed runoff observation station in Central Dian Plateau, the study on hydrological properties and water balance of plantation was conducted, and some analysis results are as follows: (1) The seasonal distribution precipitation in this area is uneven, the rainfall of wet season (from Jun. to Oct.) accounts for 80% of the yearly total, the precipitation is mainly brought by rainfall that is more than 10mm, and most of the rain intensities are less than 5.0mm·h-1. (2) The annual precipitation of the watershed is 1005.6 mm. Regarding to the precipitation distribution of crown acting surface, crown interception is 210.6 mm, and the ratio is 20.9%; the through fall precipitation is 745.3 mm,stemflow precipitation is 49.7 mm, and account for 74.2% and 4.9%, respectively. (3) Monthly change lags behind the precipitation, and the total runoff is 172.29 mm, total runoff coefficient is 17.13%, in which the surface runoff is 8.03 mm, the underground runoff is 164.26 mm; the surface runoff mainly centralizes in wet season, and one off rainfall obviously affects surface runoff (R=0.91). (4) Annual soil moisture variation is 11.2 mm, accounting for 1.1% of the total annual precipitation. But the monthly change is relatively large; the evapotranspiration is the biggest output of the system water flow, 822.1 mm water returns to the air in the form of gas phase, accounting for 81.8% of the total precipitation; among the evapotranspiration water, the direct physical evaporation capacity of crown interception is 210.6 mm, accounting for 25.6% of the total evapotranspiration.