In recent years, a large number of Moso bamboo (Phyllostachys pubescens) plantations have been abandoned, resulting in the occurrence of vegetation succession. However, the understory diversity, changes in soil properties and soil microbial community composition, and interrelationships after abandonment are still unknown. In this study, soil samples from Moso bamboo plantations with abandonment at 0, 10, 20, and 30 years were collected in a subtropical region of southeastern China. The stand structure, understory, soil properties, and soil bacterial community of Moso bamboo plantations were analyzed. The high-throughput sequencing of 16S rRNA was used to study soil bacterial community, and a partial least squares path model (PLS-PM) was constructed to express the causal relationship among different factors and soil bacterial diversity. With the increase of abandonment years, the density of Moso bamboo and litter biomass increased while the average diameter at breast height decreased. The Pielou index of the shrubs and herbs increased in 10Y (p< 0.05). The soil organic carbon, available phosphorus, and potassium increased significantly, while soil bulk density decreased significantly after abandonment. The Shannon, Simpson, and Chao1 index of soil bacterial communities increased first (10Y) and then decreased (20Y and 30Y). Further, the redundancy analysis and PLS-PM indicated that soil properties were the key factors affecting the soil bacterial diversity. Overall, these results suggested that abandonment could improve soil quality in the short term; however, it was not conducive to the sustainable development of Moso bamboo plantations in the long term.