Abstract: Antaibao open pit mine was the first large-scale joint venture open pit mine, during 20 years, several domestic and foreign research units have carried out same studies on the slope stability. In recent years, because the mode of open-underground mining have implemented in Antaibao open pit mine, it was difficult to ensure the eastern and southeast slope stability and establish the boundary under open-underground mining, which also severely affected the normal production. Trough integrated researches, pointed out that there were two failure modes of the slope under open-underground mining, and that the position of open-off cut under underground mining is the nuclear factor to ensure the slope stability. Firstly proposed to use the vertical height of safe mining between open pit mining and underground mining as criteria, and established the boundary parameter by the criteria, provided basis for ensuring the slope stability under the condition of open-underground mining.