Soil erosion model is a technical tool to calculate the soil loss and assess the efficiency of soil and water conservation practice. The universal soil loss equation (USLE) and Chinese soil loss equation (CSLE) were widely used to calculate the soil loss. The slope length in these models is significantly affected by the contributing area threshold. In this study, 210 small watersheds which area varied from 0.2 km² to 3.0 km² were selected to investigate the effect of contributing area threshold on the slope length and then the soil loss. The small watersheds are located in Northern rocky mountain area, Northwestern loess plateau, Northeastern black soil area, Southern red soil hilly area, Southwestern purple soil area, Southwestern mountainous area and Southwestern karst area. The 1:10 000 scale topographical map and 10 m×10 m DEM of the small watersheds were collected. 11 contributing area thresholds, namely, 1 000, 1 500, 2 000, 2 500, 3 000, 5 000, 7 000, 9 000, 11 000, 13 000, 15 000 m² were used to calculate the slope length and soil loss. The characteristics of slope length, soil erosion intensity and soil erosion area with the different contributing area thresholds were analyzed. The results showed that the average slope length and soil loss area firstly rose with the increase of contributing area threshold and then tended to keep constant. In the Northern rocky mountain area, Northwestern loess plateau, Northeastern black soil area, Southern red soil hilly area, Southwestern purple soil area, Southwestern mountainous area and Southwestern karst area, the average slope length with contributing area threshold of 15 000 m² was 1.53, 4.16, 1.95, 1.90, 1.69, 1.57, 1.47 times those of contributing area threshold with 1 000 m² and the soil loss area percentage with contributing area threshold of 15 000 m² was 1.20, 1.85, 1.43, 1.37, 1.77, 1.44, 1.30 times those of contributing area threshold with 1 000 m². The contributing area threshold had different effects in the different area. The average slope length and soil loss area in Northeastern black soil area was significantly affected by the contributing area threshold. The results will be helpful for calculating soil loss and for selecting the soil and water conservation practices.