Abstract: Using Bacillus subtilis fmb J as the starting strain,a mutant strain with high- yield Bacillomycin was acquired by UV mutagenesis,and Bacillomycin was applied to prevent rice from Aspergillus Flavus mildew. The results showed when the fmb J strain was irradiated by UV for 60 s and 80 s,the fatality rate separately reached85.2% and 86.8%,and the higher positive mutation rate was obtained which was 40.33% and 44.87% respectively.Under the UV irradiation time of 60 s and 80 s,a stable and high- yield strain UV60- 4 was selected out with the maximum production of Bacillomycin up to 306.31 mg / L,which was 1.32 times of the starting strain. When the temperature was 37 ℃,the addition of water was 6 m L,and the inoculation of Aspergillus flavus( 3.3 × 103 cfu / m L)was 500 μL,adding 0.15 mg / g Bacillomycin into rice can effectively inhibit mildew caused by Aspergillus flavus.