Using surface soils collected from Guyuan Ecological Experiment Station in Semi-arid Region restored by biochar for 4years as research objects, th effects of two types of biochar (locust tree bark biochar、sawdust biochar) at three different mass percentages (1%、3% and 5%) on soil bacterial community diversities and structures were investigated by using Miseq high-throughput sequencing technology. The results showed that the diversity of soil bacterial community was increased with biochar addition, and the diversities were higher in the treatment with sawdust biochar than that in the treatment with locust tree bark biochar. Further, 3% sawdust biochar addition had the best effect on bacterial community diversities, and its Shannon index was 6.22. The dominant taxa at phyla level were Actinobacteria, Proteobacteria, Chloroflexi, Acidobacteria and Saccharibacteria, with relative abundance of 76.80%~85.31%. The dominant taxa at class level were Actinobacteria, Alphaproteobacteria, Acidobacteria, with relative abundance of 48.13%~57.08%. At genus level, the relative abundance of the Bacillus, Nitrospira increased, while the relative abundance of the Pedomicrobium, Rhizobium decreased after biochar treatmetns. Hierarchical clustering and redundancy analysis (RDA) indicated that the application of biochar greatly affected the bacteria community structures. The microbial biomass carbon, water content, ammonium nitrogen (NH₄⁺-N), organic carbon contents had great influences on the variations of bacterial community structure. The heatmap of the correlation between taxa of dominant bacteria and environmental factors further indicated that NH₄⁺-N concentration was significantly correlated with Actinobacteria and Chloroflexi. Therefore, the change in NH₄⁺-N concentration caused by biochar addition was the key factor leading to the variations of soil bacterial communities.