The SO2 and NOx emission data from Tianjin pollution source survey of 2010 and industrial volatile organic compounds estimation data were used as main sources to establish Tianjin air pollutant emission inventory. The meteorological fields of Tianjin Area in January, April, July, October 2010 were simulated using MM5. Finally, CMAQ model was used and several scenarios were designed to analyze the correlation ship between the O3 concentration change and NOx and VOCs emission change. The results indicated that O3 generation in Tianjin was limited by VOCs.O3 concentration might continue to increase when more and more NOx emissions were cut down, but VOCs reduction was beneficial to O3 control. In summer, more than 40% VOCs emission was needed to be cut down to avoid the O3 increase in Tianjin. 