Abstract: The extracellular component of antagonistic bacterium JK-2, Brevibacillus brevis, was prepared under the conditions of 30℃, 170 r?min-1 and 36 h cultural time and its inhibition ability of JK-2 against Fusarium oxysporum f. sp. cubense was studied. The results showed that the antifungal activity of the extracellular component preformed a certain thermal stability, remaining more than 88.5% after treated with 60-80℃ for 1 h; but no antifungal effect was found after it was incubated under 100℃ for 1 h. The antifungal activity also remained above 77.2% at the ranges of pH 3.0 to 5.0 and pH 9.0 to 11.0 and was nonsensitive to protease K, light and ultraviolet irradiation. The optimum conditions for Jk-2 to inhibit F. oxysporum f. sp. cubense was 30 ℃ and pH 7.0.