The rationship between land slope and sheet flow erosion was studied on the base of erosion force of sheet flow The result indicated that by the erosion of sheet flow,the relationship between land slope and the amounts of erosion was a power funtion,the amounts of erosion increasing rate(dsF/ds)added with land slope and rainfall intensity.By the raindrop slope was roughly parabolie,that is there is a critical slope sk.when Sk.The amounts of erosion was increased with land slope,but when Sk,the amounts of erosion dereased with land slope.Finally,the mechanism of land slope effect on the sheet flow erosion was also analysed