Based on field hydrological data from 1995 to 2010,the article analyzed the characteristics of precipitation and its effect on soil erosion in Uuanchuan River basin,Dingxi County,Uansu Province and concluded that:Firstly,most of the rainfall occurred from May to September,while erosive rainfall concentrated in July and August.Within the 15 years,erosive rainfall days accounted for 9.53%of annual rainy days and erosive precipitation accounted for 39.41%in total amounts.Secondly,about 1123 rainy days were observed during the 15 years with a total precipitation amount of 4866.98 mm and mean precipitation of 304.19 mm.No obvious trend was found during the 15 years.The proportion of days with erosive rainfall was about 10%annually.Thirdly,a strong positive relationship were found between river runoff and soil erosion(P<0.001),both of which decreased over time.The precipitation effect on soil erosion delayed when soil was dry.Finally,because water erosion process is quite complex,rainfall amount,erosive rainfall amount,rainfall erosivity can not reflect soil erosion independently.