At present, there are limitations in the mining and construction process of the end slope of near-horizontal composite coal seam open-pit mines. Existing studies mainly focus on mining the lower coal seam, while mining the top coal seam is more difficult and has received less attention. Therefore, to address the mining of the top coal seam in the near-horizontal composite coal seams, this study analyzes the engineering geological conditions and strata occurrence characteristics of the Baorixile open-pit mine slope. A three-dimensional numerical simulation model of the end slope is constructed using FLAC^3D, and the relationship between the filling step distance and the slope stability is calculated when mining the top coal seam 1-2 with the help of the inner dump plate. The slope stability control technology and corresponding mining scheme of 1-2 coal seam in top coal seam are determined. The research findings show that the replacement step distance of the top-level coal seam in the end-slope 1-2 coal seam should not exceed 80 m. When mining the top-level coal seam in the end-slope 1-2 coal seam, the equipment is arranged on the flat plate of the inner dump extended to the bottom plate of the 1-2 coal seam. The mining method involves layered tamping and inner row tracking backfilling. By employing end slope mining, the whole region can recover 2.260×10⁷ t coal from the 1-2 seam, resulting in an income of 4.972 billion yuan.