Abstract: 6 strains exhibiting antagonistic activities against grape downy mildew blight were obtained by the method of plate observation．By the detection of metabolites, the strain BMJBN02 was provided with the optimum efficiency of cellulase,chitinase and β1,3glucanase, and its hydrolysis circle on the plant was the largest. The results showed the strain BMJBN02 was identified as Bacillus.megaterium,through analyzing its morphological,physiological and biochemical characteristics,16S rDNA sequence and phylogenetics．Using the leaf disc for screening, it was significant that area of the mold layer significantly reduced inhibitory effect in leaves treated by strain BMJBN02, with the disease incidence reduced from 100% to 42.3% and disease stage reduced from 65.3 to 18.6.

Key words: Bacillus. megaterium, antagonistic bacteria, Grape Downy Mildew, biocontrol