Abstract: The objective of this study was to study the characteristics of erosive rainfall and runoff and sediment yield in Karst area. Data were collected in a soil and water loss monitoring station in Mahuangtian of Guanling County, Guizhou province. Analyzing the data by using the empirical frequency statistics, fast clustering and discriminant clustering method, and the simple calculation method of rainfall erosivity. Results showed that erosion rainfall mainly concentrated from May to September, accounted for 9808% of the total erosive rainfall and 4883% of the total rainfall. Erosive rainfall occurred most in June. The standard of single erosive rainfall and rainfall intensity in Karst area was 1449 mm and 151 mm/h. Single erosive rainfall was divided into the following three types of rainfall, A (strong rainfall, long duration, light rain and low frequency), B (little rainfall, short duration, high rainfall intensity and high frequency) and C (medium rainfall, medium duration, medium rainfall intensity and high frequency). The runoff and sediment yield of Btype was much larger than that of A and C, and also was the easiest type produced runoff and sediment in the karst area. The erosivity R of single erosive rainfall was better reflected the variation characteristics of sediment erosion in Karst area when the PI30 replaced by PI in the R calculation formula.