Abstract: Northwest Yunnan has huge reserves of strategic mineral resources and is one of the important mineral resources development zones in China. However, the complex geological structure background makes the mining of mineral resources in this area face many difficulties, especially the stability of the open-pit slope. Taking a large open-pit slope in Northwest Yunnan as an example, based on the comprehensive analysis of the engineering geological conditions of the slope, the stope slope is divided into northeast slope, southwest slope and northwest slope. Through empirical investigation, the development laws of slope structural planes in different zones are obtained, and the slope stability of three zones is analyzed by using flat projection, and the corresponding prevention and control suggestions are put forward. The evaluation results show that the plane sliding failure of the northeast slope may occur along the fracture plane L1. The dip angle of the rock stratum of the southwest slope is smaller than that of the artificial slope, and the slope may slide along it. The northwest slope is greatly affected by F₄ large structural plane and F₁₁, F₁₂ medium structural plane. The evaluation results have important reference value for mine disaster prevention and control and zoning management.