Abstract:It is necessary to use biological control agents rightly for control plant bacterial wilt effectively. Three bacterial strains with high antagonistic activity against 5 different biovars of Ralstonia solanacearum were screened out of 569 bacterial strains from the soil of different regions, and strain BS2004 showed the strongest inhibitory effect. Antagonistic activity of strain BS2004 were conducted under the condition of bacterial suspension, bacteria-free filtrate, bacterial suspension treated with proteinase K and heat sterilization. The result showed that after proteinase K and heat treatments, bacteriostatic activity of strain BS2004 decreased significantly which indicated proteins as the main antibacterial substance. Application of BS2004 suspension on tomato plants reduced the disease incidence of tomato bacterial wilt, and the control efficiency was 66.75%. The population density of R.solanacearum in the soil indicated that the pathogen populations were significantly inhibited by strain BS2004. This bacterium was identified as Bacillus amyloliquefaciens using the colony morphology, physiological and biochemical characteristics, fatty acid methyl esters analysis and 16S rDNA sequencing.