This study investigated the fertility effect of retained trees for vegetation development on landslide area. The summed dominance ratio (SDR) and imagery analysis on the ortho-images were indexed to represent the trend of vegetation recovery. In addition, this study examined the mechanism of vegetation development using comprehensive evaluation including forest community distribution and soil seed bank analysis. The findings indicated that the principle mechanisms of vegetation expanding on landslide area included the natural seeding from parent stand, plant sprouting, the effect of micro-climate change, and wildlife seeding. Moreover, reserving the survived trees in landslide area can accelerate the succession speed into forestation and support vegetation restoration in landslide area.