The structure and diversity of soil bacterial communities in tea plantation soil is important for maintaining a healthy, fertile, and sustainable soil ecosystem. In the present study, soil bacterial communities and their diversity in ancient and modern tea plantations and forests in Jingmai, Bulang, and Nannuo mountains in the Yunnan Province were analyzed via Illumina sequencing of 16S rDNA. Soil bacterial abundance and diversity in ancient tea plantations were higher than those in modern tea plantations and forests. Operational taxonomic units (OTUs) were assigned to 47 phyla and 89 orders. Furthermore, Proteobacteria, Acidobacteria, Actinobacteria, Firmicutes, and Bacteroidetes were the dominant phyla with relative abundances of 91.86%, 82.48% and 77.08% in forest, modern, and ancient tea plantations, respectively. At the order level, both Burkholderiales and Rhizobiales were dominant with average abundances of 13.91% and 8.17%, respectively. Moreover, the relative abundance of twelve orders including Xanthomonadales, Rhodospirillales, Bacillales, Actinomycetales, and Bacteroidales, etc., were greater than 2%. Principal component analysis revealed that soil bacterial community structures among forest, modern, and ancient tea plantations were significantly different. With the exception of the Jingmai mountain, the abundances of the primarily dominant soil bacteria were in order of ancient tea plantation > modern tea plantation > forest. Thus, the soil bacterial diversity in ancient tea plantations showed an increasing trend.