Gradients and lengths of the slopes in the Lianshui River Basin, Xingguo County, Jiangxi Province were extracted using DEMs different in resolution, i.e. 10m, 25m, 50m and 100m, and analyzed for difference in accuracy difference between the DEMs in calculating the combined gradient and length, using the GIS digital terrain analysis method and the mathematical analysis method. Results show that 1) significant differences exist between slope gradients obtained by DEMs different in resolution, indicating that the gradient decreases with declining resolution and that the lower the accuracy, the greater the generalized effect on terrain information; and that the mean slope gradient obtained by DEM 100m in resolution is only 45.04% of that by DEM 10m in resolution;. 2) the slopes in the valley vary in length mainly in the range of 0~80m and their lengths elongate with declining resolution; and 3) the mean LS factor values obtained by the DEMs regardless of resolution vary in the range from 6.10 to 7.10; the combination of slope gradient and slope length factors reduces the effects of single slope gradient or single slope length factor; and as the topographic fluctuation increases in extent, the dominating role in LS factor shifts from slope gradient to slope length.