[Objective] The responses of natural and artificial grassland to different types of erosive rainfall in loess hilly region of Western China were researched to provide guidance for vegetation construction and soil erosion control in this area.[Methods] Based on the data measured in 2007-2015 from runoff plots located in Anjiagou catchment, Dingxi City, we analyzed the influences of erosive rainfall on the erosions on 20° slopes of artificial grassland and natural grassland.[Results] In the study area, the erosive rainfall mainly occurs from May to September, and is greater in July and August, and correspondingly the amount of erosion caused by it is more than 70% of the annual erosion. Erosions observed on the two different types of grassland were both finely correlated with PI₁₀. The erosive rainfall mainly refers to moderate rain and heavy rain, the amount of erosion caused by the two intensity rainfalls accounts for about 86% of the annual erosion. The erosion amounts observed in artificial and natural grassland caused by moderate & high intensity rainfalls were 90.8% and 91.2% of total erosion amount, respectively. The amount of soil erosion can well expressed by power function with PI₁₀, PI₃₀ as independent variables. Rainfall with 300 MJ·mm/(hm²·h) or greater erosivity caused the largest proportional soil erosion, for artificial and natural grasslands, the proportion was 32.3% and 33.4%, respectively; rainfall with erosivity of 50~100 MJ·mm/(hm²·h) was most frequent, the erosion amount proportions were 26.0% and 29.1% of the total observed erosions, respectively.[Conclusion] The lower amount criteria of erosive rainfall for artificial grassland(coverage of 75%~82%) and natural grassland(coverage of more than 80%) were 11.3 mm and 11.9 mm, respectively; and the maximum I₁₀ were 10.4 mm/h and 11.7 mm/h, respectively. The natural grassland has better effect of soil and water conservation than artificial grassland has.