Abstract: The effect of atmospheric turbulence and buildings on the dispersion of gaseous pollutants emitted from motor sources was investigated at the road intersection in the atmospheric boundary layer. A three dimensional model of street-canyon road intersection with vehicle emission was built up in the computationdomain, the Computational Fluid Dynamics (CFD) steady-state κ-ε turbulence model and passive scalar transportation equation were adopted to simulate theflow field and pollutant concentration field in neutral stratification accurately. The good agreement between numerical simulation and wind-tunnel experiment proved that CFD was capable to govern the pollutant dispersion process in complex situation. The analysis of simulation results showed that: ① At the same highlevel, CO concentration at road intersection and downwind street were higher than the other three streets obviously. ② In the plane at different height, maximum pollutant concentration always occurred in the streets parallel to wind direction. It showed that wind direction was a critical factor for pollutant transportation. ③Strong vortexes in the streets perpendicular to wind direction were generated by external atmospheric turbulence drive, that led to upwind CO concentration was higher than downwind CO concentration at the same height. ④The airflowmixing induced low local airflow speed and helped CO diffuse into the two streets perpendicular to the wind direction, and thus CO concentration near the ground was diluted at road intersection.