【Aim】 The invasive plant Cenchrus longispinus can grow rapidly and expand its population in nutrient-poor sandy soils, forming a single dominant community. This study analyzed the effect of C. longispinus on soil nitrogen cycle-related microbial communities to provide a theoretical basis for revealing the microbiological mechanisms of its invasion. 【Method】 High-throughput sequencing of 16S rRNA and nifH gene amplicons was applied for analyzing the differences in community structures and functions of bacteria and nitrogen-fixing microorganisms in the rhizosphere soils of C. longispinus, Elymus dahuricus, Agropyron cristatum, and Setaria viridis. 【Result】 C. longispinus could significantly elevate the levels of total nitrogen and nitrate nitrogen and reduce the contents of water-soluble nitrogen and ammonium nitrogen in soil. The results of soil high-throughput sequencing showed that Bacillus, Cyanobacteria, Nostocales, Anabaena, and Firmicutes were enriched in the nitrogen-fixing communities around the rhizosphere soil of C. longispinus. C. longispinus increased the relative abundance of Proteobacteria and decreased those of Cyanobacteria and Firmicutes, promoting its capacity for nitrogen fixation and utilization. Nitrospirota and Afipia were barely involved in nitrogen utilization by C. longispinus. 【Conclusion】 C. longispinus could affect the community structures of bacteria and nitrogen-fixing microorganisms in the rhizosphere soil of invasive areas to improve soil nitrogen for its growth.