With the increase of the urban traffic volume, a large number of tunnels have been built in many cities; the vehicle emission from the traffic tunnel has a significant impact on the surrounding environment, it has important meaning to study the impact of pollutant diffusion discharged from wind tower on the downwind environment, and to evaluate the air pollution situation and variation tendency around the wind tower. In this study, a reduced scale model of 1:200 is used for three-dimensional numerical simulation and wind tunnel test; results show that the numerical simulation result agrees well with the result of the wind tunnel test. The diffusion of pollutant discharged from the wind tower with the actual size is simulated by the computational fluid dynamics (CFD) program; results show that, the CO concentration ratios of points on building windward side to that of the wind tower outlet (C/C 0 ) are reduced to 1.211%–1.563% on the middle vertical line of building windward side at a distance of 200m when the building is 39m (10m higher than the wind tower), 0.974%–1.215% when the heights of the building and the wind tower are both 29m, and 0.654%–0.834% when the building is 19m. When C/C 0 of building windward is lower than the maximum allowable value of 2.67%, the required shortest distances between the building and the wind tower are 50, 150 and 200m for the building heights of 19, 29 and 39m, respectively. The results can be a reference for the design of wind tower of traffic tunnel and the determinations of the location and height of downwind new building.