The cutting slope soil is easily damaged by earthquakes and rainfall owing to excavation disturbance. Soil damage and strength degradation can significantly affect the slope stability. However, research on the evolution process of cutting landslide considering damage accumulation effect is insufficient. Taking the Dayangyun highway under construction affected by the Yangbi earthquake as the study area, field electrical measurements were conducted and slope damage was determined on the basis of evolution law of soil damage under rainfall, which was determined by laboratory test. A discrete element model of the damaged slope was developed, and evolution process of landslide was analyzed with different damage factors. The results indicate that trailing edge crack appears when the damage factor is 0.19. As the damage factor increases from 0.19 to 0.33, the slope body starts to slide along the fissured soil layer. The cutting slope is pushed by the upper slide body, and soil particle displacements increase from 3.5 to 39.0 m.