A physiological and psychological experiment was conducted in summer, 2008 to ascertain the effect of air flow on human thermal comfort in hot summer. The statistics analysis shows that air flow makes physiological index and thermal sensation an obvious drop tendency, which is correlated to the air temperature of indoor environment. The lower the air temperature is, the greater the physiological index and the thermal comfort drop. But when the temperature is up to about 34℃, the air flow almost does not make any change to physiological index while the human sensation is still improved. These results indicate that air flow can improve human thermal comfort to some extent, but the improvement has limits. Higher air temperature, strong wind and long time exposure to wind can lead to uncomfortableness.