In order to explore the influence of the slope of the dam surface with high working heads and large discharge per unit width on the hydraulic characteristics of an integrated energy dissipator, Ahai Hydropower Station was chosen as a prototype based on numerical study, in which a three-dimensional k-ε two-equation turbulence model was used and a gas-liquid two-phase flow VOF computing method was introduced with a geometric reconstruction format to iteratively generate free water surface. Three gradient slope ratios were simulated, including 1∶0. 80, 1∶0. 75 and 1∶0. 65. The results show that, firstly the maximum negative pressure value is located near the lower 1/4 of the first step elevation lobes and increases with the slope. The maximum negative pressure is 61. 02 kPa for the slope of 56. 98°, exceeding 6×9. 81 kPa. Secondly, the minimum cavitation number occurs at the exit point of the wide tail pier water tongue and decreases with the steepness of the slope. The minimum is 0. 358 for the slope of 56. 98°, and the maximum is 0. 381 for the slope of 51. 34°. Thirdly, as the slope of the dam surface becomes gentle, the maximum flow velocity at the bottom of the stilling pool increases, with the highest value for the slop of 51. 34°, which reaches 26. 84 m/s, exceeding 25 m/s and is prone to erosion. The maximum velocity at the bottom of the stilling pool is the smallest, being 24. 00 m/s for the slop of 56. 98°. The maximum flow velocity before the tail of the stilling pool decreases with the increase of the slope. The minimum is 9. 63 m/s for the slope of 56. 98°, and the maximum is 9. 96 m/s for the slope of 51. 34°. Finally, the slope has little effect on the energy dissipation rate of the integrated energy dissipator. The slope increases from 51. 34° to 56. 98°, but the energy dissipation rate only increases by 0. 15%.