Abstract: With the rapid development of underground coal mine support technology and equipment in China，the technology for mining open-pit coal at the end of open-pit mines using underground technology has also been gradually improved.In order to study the change law of the surface-underground combined mining disturbance on the stability of open-pit side slopes under different coal seam occurrence conditions，the coal seam occurrences under the side slope was divided into different levels according to the coal seam occurrence conditions and mining methods.Three types of sloping and backward tilting were used to theoretically analyze the failure principle of the sideslope sloping of the underground mining.A numerical model was established according to the rock mass mechanical parameters of the Anjialing Open-Pit Mine.The distribution of the high stress area，the degree of deformation and damage，and the scope of the damage were studied，and the law of slope stability changes under the same mining technology and different coal seam inclination in the open pit mine was obtained.The results show that the larger the dip angle of the coal seam，the larger the influence range of the high stress area on both sides of the working face，and the reasonable control of the distance between the open cut position and the slope surface can avoid the influence of the high stress areas on the slope stability； the greater the dip angle of the lower coal seam，the larger the scope of the slope damage after underground mining； when the coal seam is in the state of sloping occurrence，the degree of damage to the slope is greater than that in the horizontal occurrence，and the degree of damage in the state of anti-dip occurrence is less than the horizontal occurrence，the state of coal seam sloping under the end is not conducive to slope stability，and the state of coal seam sloping is favorable to slope stability.