Abstract: In order to explore the influence of coal seam spontaneous combustion process on slope stability, the slope slip process under different coal seam spontaneous combustion depths was simulated by using FLAC^3D based on the engineering background of Hequ Open-pit Coal Mine. The shortcomings of the traditional fire extinguishing methods in Hequ Open-pit Mine was analyzed, and the method of slope fire prevention and control, which is more suitable for Hequ Open-pit Mine, is proposed. The results show that: the safety coefficient of the current slope of the two non-working sides in the open pit mine is higher than the safety reserve coefficient required by the design code, which meets the requirements of safety production. The slope displacement of open-pit mine increases gradually with the expansion of spontaneous combustion range of coal seam, while the safety factor decreases gradually with the expansion of spontaneous combustion range of coal seam, and both of them show quadratic function law. The range of strain concentration zone in slope increases with the increase of spontaneous combustion degree of coal seam. The slope instability caused by spontaneous combustion of coal seam is the whole slope landslide process caused by the gradual accumulation of damage of cantilever beam in upper coal seam.