Abstract: 【Objective】To study diversity of culturable endophytic bacteria in the roots, stems and leaves in different degrees of invasion of Spartina alterniflora, and analyze their biocontrol and plant-growth-promoting activity, provide new research ideas for S. alterniflora invasion research and provide microbial resources for subsequent agricultural applications.【Method】S. alterniflora with different invasion degrees were used as the research object, and six selective media were used to isolate microorganisms by dilution coating method. 16S rRNA sequence similarity and construction of phylogenetic trees were used to determine the classification status of microorganisms. The plate confrontation method was used to detect the antagonistic activity of the bacterial strain against the pathogen of banana fusarium wilt;and the indole acetic acid production(IAA), phosphorus solubilization and nitrogen fixation were analyzed through functional plate analysis.【Result】A total of 269 endophytic bacteria were screened from the roots, stems and leaves of S. alterniflora. After deduplication according to the colony morphology and culture characteristics, the 16S rRNA sequencing and comparison of 82 strains were performed, and they belonged to 6 classes, 16 orders, 19 families and 31 genera, including 21 strains of nitrogen-fixing bacteria(25.61%), 22 strains of IAA-producing bacteria(25.61%), 11 strains of phosphate solubilizing bacteria(13.41%), 14 strains(17.07%) could antagonize the pathogen of banana fusarium wilt, and discovered potential 13 new strain species(15.85%). The degree of invasion of S. alterniflora was different, and the diversity of endophytic bacteria also changed. As the degree of invasion increased, γ-proteobacteria dominated, while the diversity of actinomycetes and bacillus increased.【Conclusion】The endophytes of S. alterniflora are rich in diversity, and mostly have life-promoting and biological control functions. They have potential application value in future agricultural production.