Abstract:Based on the systematic study on hydrological effects of mixed forest, eucalyptus forest and naked land in Xiaoliang experimental station, Guangdong Province, the profits of water and soil conservation were examined. It was shown that the total erosion rate by rainfall for naked land is 5. 2 times than that for eucalyptus forest and 228. 1 times as high as that for mixed forest,while the erosion rate by surface flow for naked land is 10. 3 and 30. 9 times higher than that for eucalyptus forest and mixed forest, respectively. The eroded components from mixed forest are mainly made up of smaller particles. There is the experimental relations X=f (PA) between erosion (x represents weight in unit of kg) and rainfall (P, mm), in which the parameter A represents the influence of precipitation on erosion. For various soils, A is different. In mixed forest, A< 1; eucalyptus forest, A= 1. 48, and naked land, A= 1. 85. Mixed forest has a larger change of erosion rate among different years. At the same time, we successfully estimated the annual erosion rate by applying the theory of "gray system"model GM (2, 1).