Abstract: This study analyzes the impact of restriction measures on urban air quality during the post-Olympic times through simulation using an integrated MM5-CMAQ modeling approach under emission reduction measure-scenarios aimed at construction works and traffic activities.Resultsshow that if daily vehicles are not restricted,the mean monthly increase ratios of PM₁₀ concentration are 6.81%,8.27%,and 7.85% during October,November,and December in 2008,respectively;and the mean monthly concentration of PM₁₀ increases by 6.88 μg/m³ in October,9.68 μg/m³ in November,and 12.10 μg/m³ in December,respectively.Besides,the periods of November 2 to 6,2005 and December 25 to 29,2007 are selected as two study cases with heavy pollution.The PM₁₀ concentration in the heavy pollution process decreases by 21.56% in November and 20.30% in December if contingency measures are conducted,with the mean concentration of PM₁₀ decreasing by 93.8 μg/m³ in November and 88.4 μg/m³ in December,respectively.During the post-Olympic times,the implementation of temporary restrictions on main local emission was helpful to improve the air quality to a certain extent in Beijing.In the long run,the long term regional environmental coordination and collaboration mechanism connected with systematic measures about local dominant emission reduction is the key to deal with the air pollution in Beijing.