Xiaojiang drainage basin locates in the upper reach of Yangtze River, China, and is one of the regions suffering from serious erosion and ecological degeneration due to the climate, geological and geomorphological conditions and the heavy human activities. Reforestation is an effective measure for the ecological restoration, which has been done sine 1980s in the region. Four kinds of pure plantations, i.e. Eucalyptus spp., Acacia mearnsii, Leucaena leucocephala and Pinus yunnanensis were investigated in the sample plots. Developing processes of species diversity and community structures of the tree layers, secondary shrub layers, and herbaceous layers were studied with the “ergodic hypothesis” method and the indexes of species richness, coverage, importance value and Shannon_Wiener index et al. And erosion control abilities of the four types of plantation were compared in this paper. The study made clear that Acacia mearnsii and Leucaena leucocephala grew faster, and had higher crown coverage and stronger erosion control ability than Pinus yunnanensis and Eucalyptus spp. Pinus yunnanensis had the highest secondary understory biodiversity, and Eucalyptus spp. had higher secondary understory biodiversity than that of Acacia mearnsii and Leucaena leucocephala mainly due to the different characters of the tree layer coverage. Different kinds of plantation had distinct effect in promoting plant diversity and had different erosion control ability. So plantation species selection and association mode should be considered in the process of reforestation for ecological restoration.