Abstract: Aiming at the 3# deformation body landslide surge in a reservoir area, we use three-dimensional numerical simulation to analyze the landslide surge propagation process in the reservoir area, and the effect of grid size on the accuracy of numerical analysis calculations is studied. Meanwhile, a 1∶280 hydraulic physical model test is established for verification, and the results are compared with the surge height calculated by the Pan's method. The results show that the calculation accuracy of numerical analysis is related to the model grid size, the severity of the surge, and the distance of the surge. The three-dimensional numerical analysis and model tests have basically the same trend of the surge height. When the surge wave spreads to the front of the dam, the error of the surge height obtained by various methods is small, and the numerical analysis results can be used as the basis for evaluating the dam safety impact. The surge formed by 3# deformation body surpasses the dam crest by about 8.37 m at the 4th peak (t=151 s), only 3.3% of the maximum dam height, and the overflow is limited, which will not pose a threat to dam safety.