Abstract: This article takes the geological disasters of avalanches and landslides in the upper mountain of a mine in Guizhou Province as an example, and uses discrete and finite element numerical analysis methods to establish two-dimensional and three-dimensional numerical calculation models of slumped mass. The change process of the stability coefficient of the upper slope of the coal mine under the action of underground excavation is calculated, and the formation mechanism of the collapse body is analyzed from the aspects of displacement, stress and strain of the mountain instability. The research results show that the underground mining activities of coal mines under natural conditions have an impact on the stability of the upper mountain. When the local underground coal mining activities are close to the mountain, the mining activities have little effect on the stability of the mountain. However, when the mining activities are carried out in the lower part of the mountain, its influence on the stability of the mountain gradually increases, which shows that underground mining activities are one of the main factors leading to the occurrence of avalanche disasters in the upper mountain of a mine in Guizhou Province.