Abstract: In order to study the diversity characteristics of Brevibacillus brevis strains isolated from different areas and to screen the biocontrol strains which produce volatile substances, the genetic diversity of Brevibacillus brevis strains was analyzed by using REP-PCR, BOX-PCR and ERIC-PCR, and the biocontrol strains which produced volatile substances were screened by using two-compartment plates. The results showed that 11-15 bright and stable bands could be amplified with BOX, ERIC and REP primers, and the polymorphism rates reached 85.71%, 93.33% and 90.91%, respectively, indicating that there were rich genetic diversity in the genomes of Brevibacillus brevis strains isolated from different regions. The hierarchical cluster analysis results showed that:20 strains of Brevibacillus brevis could be divided into three groups when λ=4.02. Of these clusters, 75% of the strains which were collected from Qinghai were gathered in group Ⅱ, 75% of the strains which were collected from Tibet were gathered in the first subgroup of group Ⅲ, and all the strains which were collected from Zhangzhou in Fujian were gathered in the second subgroup of group Ⅲ. By using two-compartment plates, 5 strains of Brevibacillus brevis were screened, by which the volatile substances produced had significant inhibiting effect on Lasiodiplodia theobromae FJAT-3586, and the bacteriostasis rates of FJAT-18569 and FJAT-18570 were 62.80% and 59.85%, respectively. This study provided some basis for studying the polymorphism of Brevibacillus brevis and laid a foundation for expanding the microbial resources for biological control of postharvest fruit diseases.