Abstract: Established the position of A178 strains based on the results of morphologic characteristics, physiological and biochemical properties and phylogenetic analysis of 16SrDNA sequence.eventually A178 was identified as Bacillus subtilis.And A178showed stronger antagonism against Rhizoctonia solani ,Fusarium oxysporum f．sp．vasinfectum and Verticillium dahliaeon by plate duel culture. And the examination of antagonistic mechanism under light microscope showed that antagonistic substance of A178 appeared to inhibit pathogens by leading to mycelium rupture, distortion, abnormality, and inhibition bourgeon of conidiophore ,and leading to abnormality of conidiophore.