In this paper, the sensitivity of Gram-negative bacteria, Gram-positive bacteria, yeast, fungal spores and Bacillus cereus spores of several food borne microorganisms in the relative humidity of 90% and 0.08 mg/L gaseous ClO₂ was studied. The results showed that the resistance of Gram-negative bacteria, Gram-positive bacteria, yeast, fungal spores and Bacillus cereus spores to gaseous ClO₂ gradually increased. Through the treatment of gaseous ClO₂, the average reduction of microorganism was 0.1~3.5 lg (CFU/cm²). At the same time, the effects of starch, fat, protein and NaCl in food on the antibacterial activity of gaseous ClO₂ were also studied. Different concentrations of soluble starch, corn oil, butter, whey protein isolate and NaCl were added to the agar medium, and the Leuconostoc was inoculated to the agar plate, and then treated with ClO₂. The results showed that soluble starch and NaCl had no significant effect on the antibacterial efficiency of ClO₂. However, butter, corn oil or whey protein in agar almost eliminated the antibacterial effect of ClO₂. The peroxide value of corn oil emulsion treated with gaseous ClO₂ increased significantly, indicating that the first oxidation product was formed. Similarly, treatment with ClO₂ can increase the carbonyl content of whey protein and induce the transformation of SH group to S-S-group. The results show that gaseous ClO₂ is an efficient decontamination agent for carbohydrate rich foods, but its decontamination effect for high protein and fat foods is limited.