The process of runoff and sediment yield in bareland and Astragulus adsurgens of different coverage were studied by means of artificial simulated rainfall. The results showed; the process of runoff and sediment yield were exponential (ｙ＝ｅａ＋ｂｘ) distribution in bareland, and were power (y=axb) distribution in Astragulus adsurgens grassland. When coverage varied from high to low, the parameter a decreasing, and b increasing.