As one of the most important soil and water conservation engineering measures, the check dam plays an important role in the process of soil erosion control on the Loess Plateau of China. Combined with the hydrodynamic model, the regulation effects of runoff and erosion hydrodynamics on check dams was studied under different precipitation types in the Xiliugou watershed of Loess Plateau. The Xiliugou watershed is dominated by the four precipitation types, short duration and small total amounts (P1), long duration and small total amounts (small total amounts), short duration and larger total amounts (P3) and short duration and largest total amounts (P4). The results show that the peak flow time may lag behind in the upper and middle reaches, while it may be advanced in the downstream in the parallel layout of the dam system watershed. The check dam system plays a significant role in reducing runoff and erosion hydrodynamics. The construction of check dams results in a significant reduction in the peak flow under the P2 precipitation type, reaching 39.41%. For the average maximum velocity, runoff shear stress and runoff power along the main channel, the P2 precipitation type results in a significant reduction in hydrodynamics in the dam system watershed, reaching 16.72%, 21.44% and 33.10%, respectively. However, for peak velocity, runoff shear stress and runoff power along the main channel, the P3 precipitation type results in a significant reduction in hydrodynamics in the dam system watershed, reaching 14.34%, 19.99% and 31.42%, respectively. The regulation effect of the check dam system on erosion hydrodynamics is stronger in the middle reaches and gradually weakened in the lower reaches of the watershed.