Abstract: In view of progressive failure in landslide instability of cohesive slope under the self-weight service during the excavation process，with the method of PFC2D numerical experiments，the whole process is generated from growth，development and evolution to the final slide of the cohesive slope. Combining with the energy dissipation structure，it is pointed out that the landslide failure process under self-weight service is essentially a state instability phenomenon caused by energy dissipation driven by energy release. The interaction between energy release and energy dissipation is the internal cause for progressive failure of landslide. The whole process of landslide divides into 3 stages，namely the creep damage，loss of strength，crack development，landslide acceleration，landslide deceleration，sliding surface enlarging. The strength slope instability criterion based on energy release is given from Meso-scale particles，and further the essential reason for the whole landslide damage is described.

Key words: Cohesive slope, Progressive failure, Particle flow code 2D, Energy dissipation structure, Strength slope instability criterion