The stability of mine slope is a major safety and production problem that affects mining practice. A safe environment is an important prerequisite for mining. Therefore, mine slope stability analysis has important guiding significance for safety production. This paper takes the Huanghua limestone mine slope in Chongqing as an example to perform a numerical modeling analysis. Firstly, the unmanned aerial vehicle (UAV) was used to obtain the geometric shape of the mine slope and identify the rock structure surface, and a 3D geologic model was created based on photographic identification results. Then, the finite element strength reduction method was used to compare the stability of the slope of the mine under natural condition and heavy rain condition, and the influences of rainfall on slope stability were revealed. The results show that under the condition of heavy rain, the slope deformation and strain are larger than those under natural conditions, and the safety factor is smaller. Specifically, the deformation and strain under heavy rain are 30% and 40%-60% higher than that under natural condition. The safety coefficient decreased by 5%-7%, and the numerical simulation results were basically reasonable. The stability of the mine slope is high, and the possibility of overall slip failure is low. However, the risk of local block falls should be prevented, and further research is needed to determine whether local slope reinforcement is required. In addition, the research results of this article verified the applicability and reliability of the comprehensive research methods of on-site investigation, lab testing, preliminary determination of 3D models, and key analysis of 2D profiles for evaluating the stability of rock slopes.