The universal soil loss equation (USLE) and Chinese soil loss equation (CSLE) are widely used for soil erosion evaluation. Different methods for calculating slope length factor could cause differences in topographic factors and soil erosion. The purpose of this study was to evaluate the effects of different methods for calculating slope length factor (L) on topographic factor and then on the soil erosion. The 1:10 000 topographic maps from five regions of Nenjiang, Wuqi, Kaixian, Huailai and Changting were selected and 5 m×5 m DEMs were generated. The segment slope length method (SSLM) and the catchment area method (CAM) were used to calculate the slope length factor. The CSLE was used to calculate soil erosion. The results showed that the average L factor value and spatial variation from the CAM were greater than those from the SSLM. The area with low L factor values had less difference and the area with high L factor value greater difference between the two methods. The proportions of soil erosion area calculated by the two methods in different terrain areas were not obviously different. However, the soil erosion intensities showed significant differences between the two methods. The results could provide data support and theoretical basis for the study of soil erosion topographic factors and soil erosion assessment in different topographic regions.