Abstract: The inhibitive effect, thermostability, pH stability and action mechanism of the metabolite of Streptomyce spp. R15 were primarily studied. The results showed that the metabolite of R15 exhibit strong inhibition on the spores germination of Fusarium oxysporum f.sp. vasinfectum, inhibition rate was 98.37%. The germ tubes of spores of the Alternaria alternate were swollen then stopped growing after treated with the metabolite; the conidia of Colletotrichum nicotianae could germinate but not form appressoria, the germ tubes formed apophysises in their top end. The hypha of P. parasitica and P. capsici were aberrance, twisted and cell wall was disintegrated. By means of twisting, penetrating and clinging, R15 hyperparasited on the hypha of the P. parasitica, the hypha of P. parasitica was broken. The metabolite was stable with heat and pH. The metabolite had better inhibitive effect when it was at temperature 20~55℃, pH 3~9.