Abstract: In order to investigate the difference of bacterial community structure between upper soil and lower soil and the driving effect of bacteria on the function of soil, 16S rRNA gene high-throughput sequencing and soil nutrient determination methods were used to analyze the 0-20 cm and 20-40 cm soil layers of Betula platyphylla forest at 40 ages in Sumushan Mountain. The results showed that the content of organic matter and the activity of polyphenol oxidase in the upper soil of Betula platyphylla forest significantly increased by 75.25% and 120.45% compared with the lower soil. Shannon diversity（5.83） of bacteria in upper soil was significantly higher than that in lower soil（5.74）. Actinobacteria, Proteobacteria and Acidobacteria（relative abundance＞15%）, Xanthobacteraceae（relative abundance＞7%）, Bradyrhizobium, Sphingomonas, Pedomicrobium, and Mycobacterium, Nocardioides, Solirubrobacter and Gaiella（relative abundance＞1%） belonged to Actinobacteria were the dominant bacterial groups in Betula platyphylla forest. Verrucobacteria（Linear Discriminate Analysis, LDA 4.07）, Bacteroides（LDA 3.80）, and Nocardioides（LDA 3.72） and Oryzihumus（LDA 3.48） belonged to Actinobacteria were the main bacterial phylum and genus contributing to the difference between the upper and lower soil of Betula platyphylla forest. Polyphenol oxidase activity, alkaline protease activity and organic matter content were the main environmental factors affecting the bacterial community structure of Betula platyphylla forest, and significantly affected the Actinobacteria bacteria. In conclusion, there were significant differences in bacterial diversity between the upper and lower layers of soil in Betula platyphylla forest. Actinobacteria improved the fertility level of forest land as an important bacterial group by promoting soil carbon cycling in Betula platyphylla forest, and promoted the healthy and stable development of soil ecosystem in Betula platyphylla forest.