Abstract: This paper presents the effects of forest to the hydrological characteristics with three scales,including the runoff section,the natural slope runoff sites,and the watershed.The results show that:in the experimental watershed,annual runoff coefficient was 43.12% in 2004 and 10.43% in 2005 while sediment yields was zero.Runoff coefficient had significant correlation with rainfall and there was a relation of a conic curve.Comparing the natural slope runoff sites in the forest land and non-forest land,the maximum value of annual runoff coefficient in the forest land was 0.72 in 2003,while one in the non-forest land was 0.97 in 2004.The sediment modulus of natural slope runoff in the forest land significantly dropped.Sediment subduction in the forest land was 18.7% in 2004 and 77.3% in 2005.The order of runoff amount was Castanea mollissina>Robinia pseudoacacia>Pinus tabulaeformis in the runoff plot of different trees.By sampling inspection on water quality of watershed,the results show that most indexes of water quality achieved the national standards of Ⅰ class,while over-leveled indexes were total N content and total P content.In general,with the increasing the forest coverage in the watershed,the function of flood control,water retention,sediment reduction,and improvement of water quality could be strengthened obviously.