Abstract: The geological model of slope was established by taking the northern end of Baorixile Open-pit Mine as the research object. Based on the hydrothermal coupling theory, the thickness changes of frozen layer under different temperatures were analyzed by COMSOL finite element analysis software. GEO-slope software is used to analyze the slope stability under different thicknesses, revealing the influence law of slope angle change on slope stability, and determining the reasonable slope angle of slope mining in freezing period. The results show that the optimum mining period is from mid-February to mid-March, when the maximum frozen layer thickness is about 3.4 m. Under the action of 3.4 m frozen layer, the stability coefficient of slope in frozen period increases by 7.3% compared with that in non-frozen period. During the freezing period, the reasonable slope angle is 29°, and more than 84,000 t coal can be recovered. A transitional measure of increasing the width of the inner row step to 40 m is proposed to ensure the safety of the transition from freezing period to thawing period.