A total of 276 endophytic bacteria isolated from soybean nodules were used to study antagonistic effect against Alternaria alternate,and characterized by cultural characteristics,cell morphological observation,16S rDNA sequencing,phylogenies and saline-alkali resistance test.The results indicated that nine of the endophytes have the most obvious inhibitory effect by the first and the second screening.Combined with the colony characteristics,cell morphological characteristics,16S rDNA sequencing and phylogenetic analysis,Strain DD029,DD201 belong to Pseudomonas,DD052 belongs to Sinorhizobium,DD166 belongs to Stenotrophomonas and DD007,DD174,DD179 belong to the genus Bacillus.Antagonistic experiments showed that the hyphae of Alternaria alternate grew more branches,the growth end appeared coralline branch with deformity,suggesting that allelochemicals such asantibiotics,sterilizable volatile substances produced by endophytes during the development and metabolic process,maybe inhibit the development of pathogens hyphae.In addation,it may also be attribute to the fast growth of endophytic bacteria,occupy the space formation of nutrition,nutrition competition on the pathogen,cause the pathogen and the distortion due to the lack of nutrition.Another,endophytic bacteria potentially produced biofilm and rapidly covered medium surface,and produced extracellular metabolites to hinder the pathogen growth and extension of hyphae.The results of saline-alkali resistance testshowed that the delay period and logarithmic phase of strain DD029 and DD254 show extension with the increase of salt concentration,but DD029 can tolerate 5%salt concentration and DD254 tolerate 4%salt concentration.The salt liquid medium presented white pellicle(Biofilm),maybe it is a salt resistant physiological mechanism of the endophytic bacteria to salt stress environment.