Abstract: This study takes the adjacent slopes of a certain mine as the engineering background. Based on field structural plane surveys, borehole RQD statistics, RMR rock mass quality evaluation, and parameter reduction using the Hoek-Brown strength criterion, a three-dimensional geological model of the strata, faults, and current/final pit limits of the adjacent slopes was constructed. The 3DMine−Rhino−Griddle−FLAC3D coupled process was employed to analyze the stress field, displacement field, plastic zone, and point safety factor distribution of the adjacent slopes. Furthermore, PFC3D was used to simulate the rockfall movement of fragmented hazardous rock masses and the protective performance of passive protective nets, and the effectiveness of the protective measures was evaluated. The results indicate that the current slopes are overall stable and do not pose a significant risk of large-scale collapse. Displacements are relatively concentrated at the southern end and northern corner of the final slope junction, but the plastic zones do not form a continuous failure zone, and the point safety factors indicate that the slopes remain stable overall. Without protection, 88.00 % of the rockfalls remain on the first bench, and 8.00 % may roll down to the third bench or below. After 2 m and 3 m passive protective nets are installed, the retention ratios on the first bench increase to 98.30% and 99.17 %, respectively, significantly reducing the risk of long-distance rockfall. The research results can provide references for the stability evaluation of adjacent open-pit mine slopes, zoned protection against rockfall hazards, and subsequent safety production management.