Taking Jiuyuan valley in the loess hill and gully area as a test site,the accuracy of terrain variables derived from 1∶50000 scaled DEMs by means of a careful comparison with high accuracy DEMsof 1∶10000 scaled is probed into. The experiment shows a big error between the terrain variables(i. e. slope gradient,surface curvature,channel networks etc. derived from the both information sources. At present,1∶50 000 scaled DEM has been set up in the whole country,which will be applied as an important base for soil erosion investigation as well as soil and water conservation project planning in the loess plateau region.