【Objective】Great differences exist in the utilization of carbon and nutrients between habitat generalists and specialists, which play unique roles in the cycle of soil energy and nutrients. At present, the research on farmland microorganisms mainly focuses on the whole bacteria, fungi, archaea or other functional communities, and the understanding of habitat generalists and specialists in farmland ecosystems is still lacking. Therefore, this study was designed to explore the community structure, assembly mechanism and possible functions of habitat generalists and specialists in typical paddy soils in eastern and southwestern China. 【Method】Sixteen surface soil samples (0~20 cm) were collected from the eastern area (Jiangsu, Anhui, Shanghai) and southwestern area (Guizhou and Yunnan) of China according to the data of the second soil survey, and their physico-chemical properties and next generation high-throughput sequencing were analyzed. 【Result】The results showed that 3.28% of all OTUs were classified as habitat generalists while 9.07% as habitat specialists. There were significant differences in species composition between habitat generalists and specialists. At the level of phylum, the proportions of habitat specialists in Chloroflexi, Actinobacteria, Nitrospirae, Firmicutes and Planctomycetes were higher than those of habitat generalists. The analysis of the community assembly process based on the β diversity null model showed that habitat generalists and specialists were dominated by deterministic process. Compared with habitat specialists, habitat generalists were more affected by the stochastic process. The environmental factors driving the community structure variation of habitat generalists and specialists were different. pH, mean annual precipitation, clay content and total nitrogen were the main factors driving the community structure variation of habitat generalists, while the community structure variation of habitat specialists was dominated by pH and clay content. By analyzing the co-occurrence network and robustness of habitat generalists and specialists, it was found that the habitat specialists’ network had more connections, more complexed structure and stronger robustness. The functional prediction by FAPROTAX showed that biological nitrogen fixation mainly existed in habitat generalists. 【Conclusion】Information derived from the community structure, environmental driving factors, assembly process, co-occurrence network characteristics and related functions of nitrogen metabolism of habitat generalists and specialists, provides a theoretical basis for the evolution and regulation of bacterial communities in paddy fields.