Abstract: The influences of air characteristics such as pressure, temperature and relative humidity on the thermal state of flue gas, the formation of wet plume, and on the effectiveness of wet plume control technologies were analyzed. Results showed that air characteristics would affect the selection of temperature and humidity of the saturated flue gas. The temperature of air had a greater effect on wet plume than its relative humidity. In addition, the influence of air pressure on gas emission temperature increased with the decrease of the temperature of the saturated wet flue gas. The lower the temperature of the air was, the smaller the reference change rate of gas emission temperature would be. Air temperature and relative humidity would affect white smoke elimination effect and the desired effect would then determine the condensation and reheating temperature of flue gas.