Abstract: In order to investigate the effect of the mitigation measures implemented to improve the air quality in Tianjin during 2014 APEC, the air pollution was observed in three monitoring stations in different urban function areas. Using the observed data, the air quality situation and the change of air pollutant concentrations between the same period of 2013 and 2014, and between during- and post-conference periods were compared. The change of ratios among different species was compared as well. Backward trajectory analysis was applied to analyze the origins and transporting process of air pollutants during typical pollution episodes. Results showed that the air quality in urban area of Tianjin during 2014 APEC was significantly improved in comparison with that in the same period of 2013, where the average concentrations of NO₂, PM₁₀, PM_2.5, SO₂ and CO were respectively reduced by 20.3%, 41.2%, 23.6%, 52.2% and 6.9%. However, because of the impaction from transported polluted air masses, the air quality of background site was worse than that in 2013.