Abstract: The landform of the inner dump in the grassland open-pit coal mine is affected by factors such as the shaping method and the amount of earthwork in the mining-dumping-reclaiming activities, and it faces ecological and environmental problems such as landscape fragmentation and soil erosion. Based on the existing technologies and the team's achievements, in order to further realize the integration of the reshaped landform and the surrounding hydrology in the mining area, an optimization model for the delineation of the mining complex sub-area based on the hydrological preservation surface (HPCS) was constructed. Taking the inner dump site in the Heishan open-pit coal mine in Xinjiang as an example, the optimized near-natural design landform under HPCS (MNNDL_HPCS) was used as the experimental group, and the NNDL_HPCS, the original natural landform (PNL) and the traditional design landform (TDL) were used as the control group. Combined with spatial superposition analysis and geomorphological evolution simulation technology, the optimization effects of the MNNDL_HPCS in hydrological integration, earthwork allocation and soil water erosion resistance were evaluated. The result shows: ① in the delineation of the mining sub-area, except for the adjustment of the location of the mining sub-area in the MNNDL_HPCS, the positions of the rest of the areas remain unchanged. ② Compared with hydrological fusion, with the PNL as the benchmark, the MNNDL_HPCS has the best visual effect. Specifically, the spatial overlap rate of hydrological channels is 52.84% higher than that of the NNDL_HPCS and 66.66% higher than that of the TDL; the index of hydrological fusion rate is 7.04% higher than that of the NNDL_HPCS and 18.11% higher than that of the TDL. ③ Compared with earthwork deployment, the average earthwork distance of the MNNDL_HPCS is about 0.98 m/m³ shorter than that of the NNDL_HPCS, and about 4.93% higher than that of the TDL. Therefore, the earth moving cost is slightly lower than that before optimization. ④ Comparing soil water erosion resistance, the MNNDL_HPCS can reduce the total amount of soil water erosion by about 31.65%, 56.86% and 80.59% over 10 years compared with the PNL, NNDL_HPCS and TDL, respectively. In addition, the average slope mitigation (0.28°) is the main reason why the soil water erosion resistance of the MNNDL_HPCS is better than that of the PNL, which is realized by the slope mitigation optimization module in the HPCS model. The research results can restore the original runoff channels and original landforms and landscapes in the mining area to the maximum extent, improve the stability of ecological restoration in the mining area.