Abstract: A biocontrol bacterial strain B40-3 antagonistic to Phytophthora parasitica var. nicotianae, a pathogen of tobacco black shrank, was isolated from tobacco-growing field by dual culture. The isolate had 0.9 cm fungistasis band and 2.3 cm inhibitory radius when it co-cultured with the pathogen for 3 days. B40-3 could inhibit other 13 fungal pathogens as well. In LB broth medium, its OD600 value reached to the maximum at 37 ℃, 210 rpm for 40 hours. B40-3 was identified as Bacillus subtilis by the traditional spore staining and physiological and biochemical reactions.