Abstract: Taking the stopes of No.I and No.VI ore bodies in the transition stage from open-pit to un‐ derground in Tongshankou Copper Mine as the research object，in view of the drastic changes of engineer‐ ing geological environment and the challenges of stope stability in this stage，the research on stope stability is carried out to provide theoretical support for mine stope design，support optimization and safe produc‐ tion. Through rock mechanics test and engineering geological test，the physical and mechanical parameters and engineering geological characteristics of various ore rocks such as porphyry and skarn are obtained. The quality of ore rock is evaluated by RMR method and Q classification method. The results show that the quality of porphyry and marble in No.I ore body is excellent，which is Grade II rock mass，and skarn is Grade III. The porphyry quality of the No.VI orebody is poor，which is a Grade III rock mass，and the RQD value is only 30 %，which is in a medium weathering state，which is a weak link in stability. Com‐ bined with Mathews stability chart method and Q system empirical formula，the stability of stope exposed surface is analyzed，and the key parameters are determined. The safety span of No.I orebody without sup‐ port is 12.36~15.45 m，and that of No.VI orebody is 9.49~11.86 m. The research shows that the stope of No. I ore body is stable as a whole，and the mining without support or weak support with a span of nearly 15 m can be adopted. The VI ore body needs to strictly control the stope parameters and take active support. The integrated technical route of 'evaluation-analysis-design' constructed in this study solves the practical problems of mines and provides reference for the transformation of similar mines.

Key words: open-pit to underground, stope stability, rock mechanics test, quality evaluation of orebody