One antagonistic bacterial strain ATB4 was isolated from the rhizosphere soil samples of healthy ginseng.Based on phylogenetic analyses of 16S rDNA and gyrA gene sequences, and morphological, physiological, biochemical characterizations, the strain ATB4 was identified as Bacillus methylotrophicus. The single factor experiment and orthogonal experiment were adopted to optimize the liquid fermentation medium and conditions that enhance its bio-control efficacy against Cylindrocarpon destructans caused ginseng rusted root. The best compositions of cultural medium were as follow: 3% glucose, 4% yeast extract powder, 0.05% Mn SO₄·7H₂O and 0.1% K₂HPO₄. The optimal fermentation conditions were as follow: inoculation rate 4%, initial pH 8.0, temperature 28℃, fermentation time 24 h,and medium capacity 40 mL/250 mL.