Abstract: To acquire excellent bacterial strains against tobacco black shack (TBS) disease, an actinobacteria DL157 with high antagonistic activity was isolated from marine sponge. Strain DL157 was identified as Streptomyces violascens by morphologic observation, physiological and biochemical characterization and 16S rRNA sequence analysis. High relative control efficiency was observed in plate test, pot test and field test, with the inhibition rates being 60.28%, 69.2% and 83.5%, respectively. The hyphae cell wall structure of Phytophthora nicotianastrain were destroyed by strain DL157 through secreting protease, cellulase and pectinase, causing cell wall damage and protoplasm leakage. Therefore, the growth of P. nicotianastrain was inhibited. The seed germination and root growth of tobacco were promoted by strain DL157. And the soluble protein content and amylase activity of germinated tobacco seeds were increased. Moreover, genetic stability was observed in strain DL157 which still maintained high antagonistic activities after 50 passages. In summary, S. violascens DL157 has the potential to be applied as antimicrobial agents against TBS disease.