Abstract:The basic L-G graph theory does not take into account the possible cost advantages of underground mining, and there are certain limitations in the boundary optimization of open-pit to underground mining. Based on the analysis of the economic and reasonable stripping ratio calculated by the price method and the reserve profit comparison method, and combined with the NPV Scheduler software, this paper studies the method of boundary optimization of open-pit to underground mining, and verifies the rationality of this method through engineering examples. The research results have certain guiding significance for the determination of mining boundary of open-pit to underground mines.