This study was carried out investigate to availability of commercial microbial pesticide and antibacterial activity of isolates isolated from different mushroom media. Ten commercial microbial pesticide and EM liquid were collected from different company. EM of these one has been used for control of mushroom disease and growth promotion at the mushroom farms. The density of bacteria and yeast in EM cultural liquid was higher than those of the crude liquid. The pH values of EM showed the low acid levels(pH 3.5~3.9) by organic acid secreted from microorganism. The kinds of organic acid was acetic acid, lactic acid and succinic acid. The dominant bacteria isolated from EM liquid was Lactobactillus sp.(21 strains), Acetobacter sp.(9 strains), PaeniBacillus sp.(9 strains) and others(12 strains). The organic acid bacteria isolated from fermentation foods( was 92 strains and the dominant genus was Weissella sp.(41 strains), Leuconostoc sp.(21 strains), Enterococcus sp.(9 strains), Lactococcus sp.(9 strains) and others(12 strains). And we isolated 2,500 bacteria from oyster mushroom and button mushroom cultural media for selection of antagonistic bacteria. Thirty five strains of these isolates showed very strong antagonistic activity. These strains were identified Bacillus amyloliquefaciens, Bacillus subtilis, Brevibacterium halotolerans, Pseudomonas libanensis, Stenotrophomonas maltophilia and Alcaligenes faecalis by 16S rDNA analysis.