Abstract: Bacillus cereus BC98-I isolated from compost extracts could significantly inhibit Fusarium oxysporum f.sp. vasinfectum on sweet pepper.The relative inhibition rate of 5.0×108 cfu/mL culture of BC98-I against the pathogen in petri dishes was 91.7% ±0.5%.It also showed certain inhibition when treated at high temperature and under high press.The inhibition rate of the 5.0×108 cfu/mL treated culture was 58.3% ±2.2%.Its crude antagonistic protein was obtained by precipitation of the cell-free culture of BC98-I with (NH4)2SO4.The test showed that the diameters of inhibition zones were 12 ~27 mm after treated by the crude substance of 5 ~60 mg/mL.The microscopical observation showed that the crude antagonistic protein could cause the growth of the hyphal abnormal. It also showed great inhibition to the germination of conidia.The germinal tube produced by conidia treated by the crude antagonistic protein was shorter than the control, part of the germinal tube expanded and formed big vacuole;while the spores in control all germinated and formed long and smooth hyphae.The antagonistic protein is thermostable, resistant to trypsin, proteinase K and chloroform, partial sensitive to ultraviolet rays and ion intensity . Its active pH range is wide, from 1.0 to 11.0.