Abstract： The dynamic characterristics of succession process of undergrow th plants in different aged Chinese fir plantations were studied.The results sho wed that in accompanying stage of accidental species,undergrowth plant species a nd quantities flourished first,and the structure was very simple. In sparse stag e of undergrowth plants, species and quantities were few,and structure was simpl e. In relatively stable stage of undergrowth plants,species and quantities incre ased, and Chinese fir community formed stable 3-layer structure including Chinese fir layer,shrub layer and herb layer. In invading succession stage of un dergrowth plants, species composition and quantities flourshed again,some broad -l eaved tree species started to grow into tree layer,and the multi-species and mu lti-layer community structure was formed. The α diversity indexes of under growth plants were obviously different and fluctuated. The richness index, diver sity index and evenness index of total undergrowth plants of shrub layer were hi gher in young Chinese fir plantation. In the stage of closed forest stand, all i ndexes obviously decreased, then increased again, reaching maximal value in o ld-growth plantation. Vertical structure of species diversity showe d shrub layer>herb layer>liana plant in 3,9 and 31 year-old plantations, in 20 year-old plantation, herb layer>shrub layer>liana plant, and in old-growth Chi nese fir plantation, shrub layer>tree layer>liana plant>herb layer. Tab 3, Ref 6