The black soil in northeastern China is suffering severe soil erosion, which is greatly impacted by slope shapes. In this paper, based on the measured runoff and sediment data derived from 15 erosive rainfalls in 2014—2015 on 9 runoff plots in the Liangshigou catchment, Keshan County, the WEPP (Water Erosion Prediction Project) was used to explore the impacts of different slope shapes on soil erosion characteristics, and meaningful results were obtained. The determination coefficient (R²) and Nash-Sutcliffe efficiency (NSE) of the overall runoff depth and sediment yield simulation results were both greater than 0.5, and the model was suitable for soil erosion simulation for the black soil region under natural rainfall conditions. For both runoff depth and sediment yield, the simulation accuracies of the WEPP model decreased with increasing slope degrees. For the simulated sediment yields from different slopes, the R² and NSE decreased from 0.60 and 0.65 on 3° slope, 0.55 and 0.61 on 5° slope, and 0.48 and 0.60 on 8° slope, respectively. The soil erosion intensities were closely related to the slope shapes. The simulated runoff depths had no obvious difference on different shaped slopes, but the simulated soil erosion intensity was the highest on the straight slope, followed by the convex slope, and the smallest sediment yield on the S-shaped slope. This study can help soil erosion control for the black soil region, northeastern China.