Digital elevation model (DEM) can represent the local relief. Topographic parameters from DEMs are the basic input data for the runoff prediction. However, different resolutions of DEMs can be used to represent the local terrain approximately. Different resolutions of DEMs lead to generate multiple scale problems. This paper extracts the topographic parameters from different resolutions of DEMs in Xiaziling small watershed and analyses the effects of DEM resolution on the accuracy of slope and discharge network. The results are listed as follows: (1) The accuracy of slope and discharge network depends on the DEMs resolution. (2) 1-m DEM can represent the local terrain, and then the slope and discharge network obtained from it are very close to the real values. The both parameters obtained from 5  m DEM are relatively close to the real values. However, the other resolutions in DEMs can not reflect the real value. Thus, when the runoff prediction is reguired more accurately, the paper suggests that 1-m and 5-m DEMs could be used as the data source. When making a rough estimate or larger  scale runoff predicition, 10-m,25-m and 50-m DEMs can be used.