The soil erosion and N loss by erosion as affected by vegetation was conducted in field runoff plots for 5～6 years. The results showed that the mean runoff amounts of 9 crops, 4 grasses, 4 grass shrubs fields were of 27773,18028 and 13149 m 3/km 2·a respectively, which were 27.5%, 51.1% and 64.3% lower than bare land. Their erosion modules were 1716, 1021 and 812t/km 2·a,which were 73 0%, 92.8% and 94.3% lower respectively than the bare land respectively. Their mean loss amounts of nitrogen by sediment...