OBJECTIVE To study the influence factors acted on germicidal efficacy of a bed unit ozone sterilizer. METHODS All the experiments were carried out according to the Technical Standard for Disinfection. RESULTS After working for 20min,the concentration of ozone in disinfection packet attained to 765.21 mg/m~3,the killing rates of Staphylococcus aureus were 90.96%,95.46% or 99.35% under the relative humidity(RH) of 50%,70% or 90% at 20℃,the killing rates were 95.56%,68.36% or 66.42% at 20℃ and RH 70% in the presence of 0%,25% or 50% organic substances,the temperature and carriers had little influence on killing rate. CONCLUSIONS Considering the strong influences of relative humidity,and organic substance on ozone sterilizer,we should increase the concentration of ozone or improve the conditions of disinfection in actual use to assure the germicidal efficacy.