Abstract: Improving slope stability is one of the important ways to ensure the safe operation of open pit coal mines and improve the resource recovery rate. Through Bishop’s analysis, the derivation of the expression of slope stability coefficient of replacement layer was carried out, and the influence of depth and height of replacement layer on slope stability coefficient was analyzed by combining Geo-Slope numerical simulation to verify the derivation. The study shows that: the influence of the replacement depth on the slope stability coefficient is not obvious before the contact between the replacement layer and the slip surface and after the contact part is unchanged, and the slope stability coefficient increases when the replacement depth supports the contact between the replacement layer and the slip surface; the influence of the replacement height on the slope stability coefficient is not obvious before the contact between the replacement layer and the slip surface before the contact between the replacement layer and the slip surface, the effect of the replacement height on the slope stability coefficient is not obvious, and after the contact between the replacement layer and the slip surface exists, the replacement height and the slope stability coefficient are positively related.