By taking small watershed on the 1∶10 000 scaled topographic map of Qingshuichuan basin in the coarse sand source area of the Loess Plateau as a basic cell

terrain factors for regional soil erosion

including surface relief

variance coefficient

and contour line density

are extracted from 1∶250 000 scaled digital elevation model.The terrain factors calculated from the 1∶10 000 scaled map are regarded as truth values to fit the calculation method of terrain factors for soil erosion in each region.Results showed that only the contour line density is an appropriate index of terrain factors for regional soil erosion.The method has been applied in the lower reaches of Huangpuchuan River

with the deviation less than 10%.Such a good simulation result indicates that the method can be used as a reference to index determination in the calculation of regional terrain factor for soil erosion.