Abstract: To explore the influence of underground goaf groups on slope stability under the open-pit and underground composite mining mode, the composite slope of the Dameigou west side of the dump and quarry was taken as the research object. Six underground goaf areas of the W1 section and four underground goaf areas of the W2 section were selected as the calculation sections. The displacement and shear strain variation laws of overlying rocks after the formation of goaf areas in each working face were successively simulated and analyzed by using numerical simulation software to clarify the development characteristics of the collapse zone, fracture zone and bending subsidence zone formed by the goaf area group. Based on the distribution characteristics of the "three zones", the slope engineering geological model was constructed, and the slope stability coefficients considering and not considering the influence of the "three zones" were calculated by the limit equilibrium method. The numerical simulation analysis of slope stability was carried out in combination with the Mohr-Coulomb criterion, revealing the landslide mechanism under the influence of the goaf group. The research results show that the overlying strata in the goaf fall in a trapezoidal pattern. Moreover, with the increase in the number of goaf areas, a superimposed effect occurs, and the range of overlying strata collapse significantly expands. The potential landslide pattern of the slopes in the W1 and W2 sections is circular arc sliding. The calculated stability coefficients of the slopes without mined-out area groups and those with mined-out area groups but without considering the "three zones" effect are consistent, which are 2.038 and 2.634 respectively. After considering the "three zones" effect, the stability coefficients of the W1 and W2 sections drop to 1.637 and 1.685 respectively. The "three zones" effect formed by the mined-out area cluster is the key factor affecting the stability of the slope.