Abstract: The roof lithology of a polymetallic underground mine is different, including carbonaceous slate, rhyolitic clastic rock, tuffaceous slate, etc. In order to understand which section of the stope span is relatively stable under the roof conditions of different lithology, and to provide a reference for stope structural parameters during mining, numerical simulation was used to analyze the stope stability under different lithology and different span conditions. The results show that regardless of the lithology of the roof, as the span of the mining area increases, the roof and side walls exhibit different stages of failure processes; When the span of carbonaceous slate is 7 m, the top plate compressive stress exceeds its ultimate compressive strength, and the top plate has already been damaged. Moreover, when the span is 6-7 m, the slope of the top plate stress has increased compared to before, indicating that the top plate pressure is in an accelerated instability period between 6-7 m. Therefore, the mining span of carbonaceous slate should be stable at 6m or below; Similarly, both rhyolite clastic rocks and tuffaceous slate exhibit the same failure pattern. The span of the rhyolite clastic rock mining site should be 7 m or less, and the span of the tuffaceous slate mining site should be 6 m or less. At the same time, corresponding support measures were provided for different mining sites to ensure the safe and stable production of the mine.