Bacillus subtilis SH7 can inhibit the growth of tobacco Ralstonia solanacearum. In order to investigate the best medium and optimal fermentative condition, antagonistic protein was extracted from fermentative optimal medium by using ammonium sulphate precipitation method, and its antagonistic ability to tobacco Ralstonia solanacearum was measured. Results showed that optimal medium for SH7 was NA medium, and its optimal fermentative condition was pH 6.0, 26 ℃, 100 mL/250mL, 170 r/min, 96 h shaking culture. The antagonistic protein was insensitive to alkaline, and at pH 9.0 or 10.0, its antagonistic ability was 86% and 88%, respectively. At 100 and 121 ℃, 20 min, antagonistic ability was 83.1% and 68.0%, respectively. The control effect of the crude protein to tobacco bacterial wilt in greenhouse was 70.8% by injection.