Abstract: Tobacco bacterial wilt is a soil-borne disease caused by Ralstonia solanaceanm. A strain of Actinomycete LC-7 with obvious antagonistic activities against R. solanaceanm was isolated from healthy soils and identified as Streptomyces sp. The fermentation broth of Streptomyces sp. LC-7 was extracted with chloroform and n-butanol. The analysis through the Czech eight solvent systems revealed that the antibacterial substance was an alkaline water-soluble antibiotic. The antibacterial material was purified by exchange column, and precipitated with alcohol to obtain the crystal. The crystal was further purified by HPLC and analyzed by mass spectrometry. The results showed that the antimicrobial active substance was a new aminoglycoside antibiotic with a molecular weight of 365.1. In the field experiment, Streptomyces sp. LC-7 had significant control effect on tobacco bacterial wilt. The control efficacy was 85.48%.