Volcanic lava habitats breed unique soil microbial communities. Soil bacterial diversity, community structure, and key factors influencing volcanic ecosystems were explored using soil microorganisms in new volcano soils and old volcano soils in Wudalianchi, Heilongjiang Provice. Non-volcano soils were used as the control. Using the Illumina high-throughput sequencing method, we analyzed soil bacterial community structure and diversity at three sampling sites. Combined with soil physical and chemical characteristics, environmental factors affecting the diversity of soil bacterial community in a volcanic ecosystem were analyzed. Results showed that the operational taxonomic units (OTUs) and the diversity index (the Ace index, the Chao 1 index, and the Simpson index) of bacteria presented the same trends and followed the order Non-volcano > new volcano > old volcano. The number of OTUs unique to new volcano soils, old volcano soils and Non-volcano soils were 852, 820, and 879 respectively, as well as the number of their common OTUs was 713. The three plots soils contained same 16 kinds of bacterial groups, and Proteobacteria, Acidobacteria, Actinobacteria, and Chloroflexi were the most dominant bacteria groups. Acidobacteria, Verrucomicrobia, and Rokubacteria had the highest relative abundances, whereas Patescibacteria had the lowest in the old volcanic soils. In the three plots, the soil bacterial communities had obvious spatial relationships, and their similarity in community structure varies greatly, It did not conform to the model of beta diversity, which similarity in bacterial composition gradually decreased with increasing geographical distance. We think it could be related to the volcanic eruption characteristics or magma composition. The obtained soil physicochemical properties indicated that soil pH, Soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), ammonium nitrogen (AN), and nitrate nitrogen (NN) in old volcanic soils were significantly higher than those in the new volcanic soils and non-volcanic soils, while water content and available phosphorus in the new volcanic soils were significantly lower than those in the old volcanic soils and non-volcanic soils. Volcanic eruption is a form of violent large-scale disturbance, the volcanic characteristics of eruption time and igneous rock led to differences among volcanic soils at different stages, and further led to differences among soil bacterial diversity and community structure. Pearson correlation analysis showed that soil pH significantly affected the Simpson index, the Ace index and the Chao 1 index of soil bacteria. The redundancy analysis (RDA) showed that soil nitrogen, soil pH, and SOM were the crucial factors affecting the bacterial community structure of the Wudalianchi volcanic ecosystem.