[Objective] In order to explore the effects of stand factors on the species diversity of plantation communities in different road areas, and to provide a reference for the construction and management of plantations in Chengdu road area. [Methods] This study used the typical plot method to analyze five different plantation communities (I, poplar pure forest; Ⅱ, camphor and poplar mixed forest; Ⅲ, pure camphor forest; Ⅳ, mixed forest of camphor and eucalyptus; V, eucalyptus grandis forest) to investigate the stand factors and species diversity of understory vegetation. [Results] (1) A total of 184 plant species belonging to 72 families and 132 genera were recorded in the study area. The number of plant species in the tree-shrub-grass layer of five different plantation forest communities varied from herb layer > shrub layer > tree layer, among which the number of understory species recorded in the pure camphor forest; was the highest. (2) The importance values of Broussonetia papyrifera and Humulus scandens dominated the shrub layer and herb layer of different plantation forest communities, respectively. (3) Among the five different plantation forest communities, the shrub species richness index D of pure camphor forest was significantly higher than that of the other communities(P<0.05); the Shannon-Wiener index H, Simpson index H′ and D size of the herbaceous layer had the same trend of change, which showed that the community: Ⅲ>Ⅳ>I>I>I>V, of which H of pure camphor forest was significantly higher than that of the other communities except mixed forest of camphor and eucalyptus(P<0.05). (4) The results of redundancy analysis showed that the average crown width in the tree layer was significantly positively correlated with D and H in shrub layer, H, H'', D and Jsw in herbaceous layer (P<0.01), and negatively correlated with H'' and Jsw in shrub layer (P<0.01). The average height under branches in the tree layer was significantly positively correlated with H, H'', D, and Jsw in shrub layer (P<0.01). [Conclusion] The study concluded that tree species composition, average undershoot height and average crown width of the tree layer significantly affected the species diversity of plantation communities in the road area, and the selection of appropriate tree species and regular pruning management would be conducive to the formation of good tree and shrub community structure and the maintenance of understory vegetation species diversity in road plantations.