Abstract: In order to reveal the response mechanism of microbial communities to pH values, we collected natural pH gradient soil, characterized their physicochemical properties, analyzed the structure and composition of the bacterial communities, and identified key factors that caused differences of bacterial community structure and composition in different environments. The results show that soil pH value is negatively correlated with the relative abundance of Proteobacteria and Acidobacteria (p<0．01), and positively correlated with the relative abundance of Actinobacteria (p<0．01). There are many nodes and links of the bacterial community network in neutral and weakly alkaline soils with higher moduarity. In weakly acidic and strongly alkaline soils, there are fewer links in the bacterial community network, resulting in a lower degree of modularity. The bacterial community is directly or indirectly influenced by soil physicochemical properties.  The distribution of bacterial communities is mainly determined by soil pH value, electrical conductivity (EC), and water-soluble organic carbon (WSOC) content. Among them, soil pH value is the main environmental variable affecting bacterial communities in soils. The research results reveal the mechanism by which pH value affects soil bacterial communities, which is of great significance for a deeper understanding of soil microecology, and provides useful information for the design of land use and soil management strategies. 

Key words: soil,  , bacterial community,  , high-throughput sequencing,  , pH gradient,  , structural equation model,  , coexistence network