Taking Jiuyuan watershed in Suide county of northern Shaanxi province，a test area, applying overlaidand cxun parative laws as a basic research m ethodology and 1:10 000 DEM as a cntenon, a research on the errors simulation and the rectify method in deriving slope gradient from 1:50 000 scale DEMs was made A gradient correction down}caling model obtained can effectively rectify the slope statistical values in the hill and gully area of the loess plateau, which is of great significance in enacting related standards in the fields of both soil erosion monitoting and soil conservation.