Abstract: To make the slope stability evaluation of open-pit mines more scientific and reasonable, and the evaluation results more reliable, it is urgent to optimize and improve the existing evaluation models. Based on variable weight theory, grey correlation theory (GRA), and approximate ideal solution (TOPSIS), an improved GRA-TOPSIS evaluation model for open-pit mine slope stability was proposed. A comprehensive evaluation index system for the stability of rock slopes in open-pit mines was constructed by selecting 12 typical influencing factors from three aspects, including geology, environment, and engineering. The variable weight theory was applied to determine the weight of indicators, and the comprehensive evaluation of the stability of rock slopes in open-pit mines was realized by calculating the gray correlation degree. Three mines (K₁－K₃) were taken as an example to verify the applicability of the evaluation model. The results showed that the slope stability of the three open-pit mines was ranked as K₃>K₂>K₁, with their stability levels of Ⅲ, Ⅱ, and Ⅱ in consistent with the actual slope conditions. The evaluation results of the improved GRA-TOPSIS model was compared with that of GRA, TOPSIS and other models. Its accuracy and superiority in the evaluation of open-pit mine slope stability were verified, reflecting its value for research. This article provides a new idea for evaluating open-pit mine slope stability.