The open stoping method is mostly used in small and medium-sized iron mines with medium stability of ore and rock. In practical application, it is easy to induce large-scale caving of roof and surrounding rocks in goaf, which seriously threatens the safety production of mines. The complex and irregular goaf group left over by the open stoping method in Zhuba Iron Mine in Nanjiang city was taken as the research object. Through surface point cloud data obtained by high-precision UAV aerial photography, combined with the mine production plan maps, a refined three-dimensional numerical model of the ore and rock was constructed, and the dynamic evolution laws of the mechanical characteristics of the surrounding rock of the goaf groups were studied. The following conclusions are obtained. The height, volume, area, and quantity of the goaf at the 1 318 m middle section are all the maximum values, which are the key factors restricting the safe mining of the lower ore body. The residual ore body at the 1 318 m middle section and the residual horizontal pillar directly facing the goafs at the 1 258 m middle section are not suitable for mining. To ensure the safe mining of the lower ore body, a systematic protection scheme for the caving hazards and impact airwave hazard of the goaf group was proposed. The engineering practice results show that approximately 188 900 tons of ore were recovered from the 1 258 m middle section, and no large-scale caving occurred in the goafs of the 1 318 m middle section during the mining period; during the mining of the central orebody of the 1 208 m middle section, caving of varying degrees occurred in the goafs of the 1 318 m and 1 258 m middle sections, but the caving hazards did not affect the production area, verifying the safety and practicality of the proposed caving hazard protection scheme.