Abstract: A total of 165 isolates with antagonistic effects against Phytophthora parasitica var. nicotianae were screened from 970 endophytic bacteria isolated from health leaves of tobacco variety NC297.Bioassay results in vivo showed that these antagonists exhibited different inhibitory activities to the pathogen which ranged from 9.55% to 55.96%.The biomass of endophytic bacteria varied not significantly during periods of seeding to maturity but the amount of antagonists increased in the growth process of tobacco.The 165 antagonists were characterized by RFLP analysis of the 16S rRNA sequence which were resulted 12 RFLP patterns.Thus,41 representative isolates,1—3 from each RFLP pattern,were selected for 16S rRNA sequencing.Phylogenetic analysis placed the 165 antagonists of P.parasitica var. nicotianae into three groups of Bacteria,namely Proteobacteria,Actinobacteria and Firmicutes.Members of the Bacillus genus in Firmicutes group were the dominant,in which 159 isolates represented by 6 RFLP patterns were associated with the species of Bacillus amyloliquefaciens subsp.plantarum,Bacillus methylotrophicu,Bacillus tequilensis,Bacillus aryabhattai,Bacillus cereus and Bacillus mycoide.And during all the 159 isolates two species,Bacillus amyloliquefaciens subsp.plantarum and Bacillus methylotrophicu,showed the highest isolated frequency.The remaining 6 isolates were respectively affiliated to the 6 species of Brevibacillus reuszeri,Streptomyces finlayi,Streptomyces atroolivaceus,Erwinia rhapontici,Enhydrobacter aerosaccus and Stenotrophomonas rhizophila.