Abstract: The species dominance and diversity index, evenness and similarity index as well as minimum area of plant communities in both sunny and shady slopes of semi-natural vegetation of Laoyangfen in Kunyu Mount were investigated. 300m2 was taken as the minimum area for tree layers of the plant communities, while 225m2 for shrub layers. There were some differences in distribution patterns of dominant species in tree layers between the two plant communities of sunny and shady slopes. It was discovered that the species diversity index in tree layer of the plant community of shady slope was higher than that of sunny slope, while the result was reversed in the shrub layers of both communities. The statistical difference between the two communities was not significant. The community evenness indexes in tree layers between both communities were of marked difference and that in the community of shady slope was higher. It was found that the similarity index in tree layer of both communities was lower than that in shrub layer. The similarity index of community based on relative coverage (RC) and relative dominance (RIV) had more meanings for analysis of structures and functions of tree layer.