Abstract: Overall slope angle（ＯＳＡ） is a key factor for the conversion of coal resources into reserves. The determination of OSA depends on slope stability analysis. In order to meet the listing requirements of HKEX, a series of slope stability study tasks, including data collection, rock testing and numerical analysis, were carried out for Bailitan Surface Coal Mine. The study has determined that the potential landslide pattern is to cut off the“semicircle-linear” type of landslide that cuts the overlying rock strata along the weak layer of the carbonaceous mudstone. Based on results of limit equilibrium analysis, it is proposed that overall slope angle of 36 ° is for the height less than 280 m and the overall slope angle from 32°to 34°is for the height more than 280 m.