Abstract: To develop the Symbiotic and Epiphyte bacterium 110 from Sinonovacula constricta Lamarck,the morphological,physiological and biochemical properties of the strain were investigated and its 16 S r DNA sequences were analyzed. The univariate test and orthogonal experiment of L25( 54) were used to optimize the fermentation conditions for antibacterial activity according to inhibition zone.Symbiotic and Epiphyte bacterium 110 was identified as Bacillus subtilis. The optimal fermentation liquid media was determined as glucose 4% and peptone 2%,and the better fermentation conditions were obtained as fermentation at 35℃ for 120 h with initial p H7.The fermentation liquor fermented at the optimal conditions could also inhibit the growth of several kinds of fungus.The inhibition rate was 100 % against Mucor mucedo( L.) Brefeld,Ralstonia solanacearum and Monilia laxa,98.8%against Fusarium oxysporum of Cotton and Fusarium moniliformis,97.6% against Alternaria solani,88.3% against Trichothecium roseum( Bull.) Link,87.1% against Fusarium oxysporumf Schlecht,31% against Gerlachia nivalis( Ces.at Sacc.),8.7% against Botrytis cinerea and 9.1% against Fusarium graminearum.