Abstract: Taking chlorine dioxide (ClO2) gas as fungicide and using plate smearing method to evaluate the antibacterial effect of aspergillus flavus.The single factor experiments of chlorine dioxide concentration and action time were investigated. And 4 factors 5 levels orthogonal test which with chlorine dioxide concentration, bacteriostatic time and carrier of aspergillus flavus as the test factors and with antibacterial rate as the index was devised to obtain the optimal extracting conditions based on the single factor experiment.The results showed that chlorine dioxide gas had a significant bactericidal effect on Aspergillus flavus. The factors sequences were the carrier, chlorine dioxide concentration, bacteriostatic time. The optimum process condition was listed as follows: When the concentration of ClO2 gas was 4.5mg /L and reaction time was 40min, the sterilization rate of Aspergillus flavus distributed on tartary buckwheat surfaces could reach 99.99%.On the equal condition, the sterilization rate of Aspergillus flavus distributed on wheat and common buckwheat surfaces could reach more than 90% . Therefore, the chlorine dioxide ( ClO2 ) gas had a potential for the further applications as effective fungicidal components.