Abstract: A large scale of landslide disaster occurred on June 3, 1980 at Yanchihe in Yichang city of Hubei province. Its volume is 130×10⁴m³. The landslide killed 284 people. Based on the site investigation and analysis, underground mining is an important reason of Yanchihe landslide. Considering the limitations of previous research, and the paper uses the stochastic medium theory that has been used widely in ground surface movement and deformation in diggings. The slope movement and deformation principle resulted from underground mining are illuminated with the stochastic medium theory. Combined with slope stability analysis and numerical simulation, deformation of slope movement induced by underground mining is analysed and verified. The conclusions are as follow:The underground mining caused differential settlements. The underground mining deformation exacerbated the formation of crack inside the slope, providing a channel for rainfall infiltration. Rainfall infiltration in crack caused the slip zone softening, causing the landslide.