Abstract: In fir forest of west Sichuan, several aspects of forest hydrology have been observed: Interception of precipitation by canopy, water retaining capacity of mosses and litter, variation of soil water content, evapotranspiration of vegetation cover and the flow of two comparative catchments of forest and cutting site. It shows that the fir forest has very important influence on regulating the water regime and higher water holding capacity, including increasing annual runoff, decreasing and slow down the flood peak, increasing the utilization of effective water regime and reducing the physical evaporative capacity.Abound with water-heat and light conditions in fir forest area of west Sichuan, very suitable for the development of vegetation. Meanwhile, the structure of the forest stand and the tree species indicate that most stands are overmatured forest (over 200 year) with low water regime comsumption. So, it cannot raise the timber yield by fully using water resources and improving the hydrologic influence. According to the reference of other countries, the water regime comsumption of pine tree is about 208mm, larch: 220mm, spruce: 193mm, while the fir forest request the lowest water comsumption among coniferous forests. According to our estimation the annual evapotranspiration on fir forest is quite low, occupied only 5% of the annual precipitation. Meanwhile, under existing physical conditions,it was suggested that using coniferous of high growth rate such as larch or spruce instead of the overmatured fir forest gradually. This may be of benefit both to raising the timber production and improving the hydrologic influence of the forest. For better conservation of the enviroment of the forest land, selecting cutting or sanitary cutting may be practised and the forest may be regulated by the other species with high growth rate and good hydrologic influence.