Objective　To study the effects of air disinfect ion by three methods. Methods　Air was disinfected by ultraviol et rays, pentadialdchyde and ozone, efficiency of disinfection was eval uated b y three different disinfection methods using synchronous sampling after and b efo re disinfected. Results　The peak of the bacteria background by precussion method was 10 o'clock, by the ballistic method was 9 o'clock and by the petri dish method was 10 o'clock before disinfected. Three disinfect ion methods were significantly different, efficiency of disi nfection of pentadialdchyde was the highest when it was evaluated by the precuss io n method, and recovery of bacteria was 43.4%～55.8% after disinfected 3 h our s; effect of pentadialdchyde was better than that of the ballistic method, and r ecovery of bacte ria was 21.8%～35.7% after disinfected 3 hours; effect of ultra violet ra ys was better than that of the petri dish method, and recovery of bacteria was 4 2.1%～60.6% after disinfected 3 hours. But their differences were not significan t. In t he course of experiment, temperature and relative humidity have a negative impac t on the ultraviolet ray's efficiency and almost have no impact on others. Conclusions　Disinfection method of the ultraviolet rays could be rep laced by disinfection method of pentadialdchyde and ozone.