[Objective] The stability of antimicrobial active ingredients of Bacillus subtilis B26 was studied. [Method] The Fermentation broth of B. subtilis B26 was passed through porous membrane after centrifugation,70% （NH4）2SO2 was used to carry out precipitation,and the sterile crude extracts with resistance against Fusarium decemcellulare Brick were still obtained after dialysis. Plate coated perforated method was adopted to detect the treatment stability towards crude extracts on temperature,pH,ultraviolet radiation,organic solvents and protease. [Result] The inhibition diameter of crude extracts of B. subtilis B26 after treatment at 100 ℃ was 78.2% of the treatment at room temperature,but the crude extracts of B. subtilis B26 completely lost their activity after treatment at 121 ℃; the crude extracts of B. subtilis B26 all had antimicrobial activity in the pH value range of 3-10,and the antimicrobial activity was the largest when the pH value was 7.0; when the crude extract of B. subtilis B26 was irradiated by UV light （power 20 W） for 80 min from 40 cm distance away,the antimicrobial activity of which was 78.1% of the control; when it was treated with ether,chloroform,methanol and acetone for 30 min,the antimicrobial activities of crude extracts of B. subtilis B26 were 96.4%,85.7%,82.1% and 81.5% of the control,respectively; when it was treated with proteinase K,trypsin and pepsin,the inhibition diameters of crude extracts of B. subtilis B26 were 15.2,16.2 and 16.3 mm,the antimicrobial activities were 76.7%,81.8% and 83.3% of the control,respectively. [Conclusion] The crude extracts of B. subtilis B26 had higher antimicrobial stability.
