Abstract: Based on the DEM data, the nearest neighbor resampling method was used to obtain different DEM data of different spatial scales. According to the different spatial scales DEM, the topographic factors, the watershed information extraction and the scale effect of DEM and the correlation analysis were investiged. The results showed that:(1) With the increased of the spatial scale of DEM, the average values of terrain factors, such as elevation, slope and surface roughness, showed a decreasing trend; The total length of the river network and the density of river network decreased with the increase of the spatial scale of the DEM, and the large scale DEM could not express the information of the small rivers in Karst mountain area.(2) Through the correlation analysis, the correlation between slope, surface roughness and DEM resolution was strong, and the correlation was significantly correlated with power function fitting.(3) According to the analysis of information entropy theory, the optimal resolution range of DEM was 30~120 m in the study area.