For screening antagonistic bacteria to control citrus melanose, 227 strains were isolated from soil collected in Hunan with gradient dilution method. Four strains showed obvious antagonistic effects to Diaporthe citri by using agar plate dual culture, and strain Y2 was finally screened out because its fermented filtrates diluted 5 times and 10 times could inhibition growth of mycelia by 69.85% and 61.76%, respectively. Morphological, physiological and biochemical characteristics and analysis of 16S rDNA sequence confirmed that strain Y2 is Bacillus pumilus. The optimum nitrogen source and carbon source of strain Y2 were soluble starch and peptone, respectively and the optimum fermentation conditions for strain Y2 include temperature at 28 ℃ and the rotation speed at 180 r/min. Under high temperature (80 ℃), strong acid and strong alkali conditions, the activity of the bacteriostatic substances produced by strain Y2 decreased significantly.