Abstract: The slope stability in the mine transferred from open pit to underground mining is a widely existing problem and the rational evaluation of the slope slip effect on surrounding rock at the bottom of the slope has important engineering significance for underground mining.Taking slopes formed in the process of excavation in Daye Iron Mine as project background，the sliding process of slide mass is numerically simulated with UDEC software，and the stress-strain laws of surrounding rock under the impact of sliding slope on the bottom after the slopes became unstable were studied from perspective of the stress field and displacement field.The results showed that the DEM software can effectively simulate the un-stability of sliding mass.After the un-stability occurs，the impact action mainly focuses on the foot of the northern slope and has a less impact on the mining area and the southern slope.The self-weight of sliding mass on mining area and hanging wall is obvious.On the vertical direction，the impact on surrounding rocks is weakened with the mining depth increasing.On the horizontal direction，the impact of sliding mass on the southern slopes is much lower than that on the mining area and the northern slopes.

Key words: Open-pit slope, Sliding mass, Surrounding rocks, Deformation characteristics