Abstract: This study aims to investigate the influence of underlying goaf groups on slope stability under the open-pit–underground combined mining mode. Taking the composite slope of the west dump and pit of the Dameigou Open-pit Coal Mine as the research object, six underlying goafs of working faces beneath the W1 section and four underlying goafs beneath the W2 section were selected as calculation sections. UDEC numerical simulation software was used to sequentially simulate and analyze the displacement and shear strain evolution of overburden after the formation of each working face goaf, and the development characteristics of the caving zone, fracture zone, and bending subsidence zone formed by the goaf group were identified. Based on the distribution characteristics of the "three zones" an engineering geological model of the slope was established, and the slope stability coefficients with and without considering the influence of the "three zones" were calculated using the limit equilibrium method. Based on the Mohr–Coulomb criterion, numerical simulations of slope stability were conducted to reveal the landslide mechanism under the influence of goaf groups. The results indicated that the overlying strata above the goafs exhibited trapezoidal caving, and with an increase in the number of goafs, a superposition effect occurred, significantly expanding the caving range of the overlying strata. The potential landslide modes of the slopes along the W1 and W2 sections were circular sliding. The calculated slope stability coefficients of the W1 and W2 sections were identical when goaf groups were not present and when goaf groups were present but the "three zones" effect was not considered, with values of 2.038 and 2.634, respectively. After considering the "three zones" effect, the stability coefficients decreased to 1.637 and 1.685, respectively, confirming that the "three zones" effect formed by goaf groups was a key factor affecting slope stability.