Abstract: Strength reduction method was implemented into the particle flow code (PFC2D) that is based on discrete element method (DEM)， to tackle the difficulties for the slope stability analysis based on continuum mechanics. In this regard， the ratio of average unbalanced mechanical force as the failure criteria to judge the unstable failure of slope， the cohesive force and frictional coefficient were reduced to capture the coalescence of fractures， this approach could not only qualitatively judge the local failure of the slope， but also monitor the complete instable failure process of the slope. By means of strength reduction method， safety factor could be finally calculated automatically. The proposed method was applied to the rock slope stability analysis of Heishan metal mine. Slope safety factors under different conditions were obtained respectively. The safety factors of 1.803 and 1.183 before and after the excavation of slope were obtained respectively， which agree with the expectations.

Key words: PFC2D, discrete element method, rock slope stability, strength reduction method, numerical simulation