To explore the effects of natural exclosure on the community structure of the moso bamboo forest and the diversity of understory plants, two types of moso bamboo forest (human-manage forest and natural exclosure forest) were chosen in Yuhang District, Hangzhou City, using the method of space-for-time. In this study, 4 different plots (0 years, 10 years, 20 years, and 30 years) were set up, according to the age of natural exclosure. The culm density, diameter at breast height (DBH), and understory vegetation types etc. were investigated in the field survey. The results indicated that the culm density of bamboos increased gradually with increase of exclosure age, while the average DBH of bamboo decreased significantly. The density of ≥ 2° bamboo of natural-exclosure moso bamboo forest was significantly higher than that of the intensive-managed forest (P<0.05). The density of dead bamboo increased significantly with the extension of exclosure period (P<0.05). The DBH of ≥ 2° old bamboo and dead bamboo started to decrease significantly after 20 years of natural exclosure. The species of shrubs under the moso bamboo forest with 0, 10, 20, and 30 years of natural exclosure were 68, 35, 58, 77, respectively, while the herbaceous species were 64, 23, 31, and 44, respectively. The Simpson index of shrubs with 10 years of natural exclosure was significantly lower than that of other years (P<0.05). The Shannon-Wiener index after 20 years was significantly higher than that of the early year (P<0.05). The natural exclosure can help to increase the index of Pielou (P<0.05). The Simpson index of the herbaceous plants decreased in the natural exclosure forest (P<0.05). The Shannon-Wiener index of intensive-managed forest was significantly higher than that of 20 years (P<0.05), and the Pielou index of 10 years was significantly higher than the other years (P< 0.05).