Abstract: In order to study the distribution of motor vehicle exhaust diffusion along the road in the city,we have used the wind tunnel test to study the level of motor vehicle exhaust concentration distribution of three typical sections(for the wind angle are 0°,45° and 90°) in Kunming urban area,and used the standard k-ε turbulence model and component transport equation to simulate the motor vehicle exhaust diffusion under the condition of 45°.The results of simulation and the wind tunnel test have been compared.The results show that firstly in the range of downwind 300m from road shoulder of the three typical research roads,the air quality is influenced by motor vehicle exhaust pollutant.Secondly,with the increase of sampling point distance,the pollutant concentration shows a decreasing trend in general and decreasing rate is bigger in the downwind from the research road.What's more,with the increase of vertical height,wind speed increasing with a significant change of gradient,pollutant concentration decreases and degree of diffusion is more obvious.Finally under the condition of 45°,the numerical simulation results are in good agreement with wind tunnel test data.