We examine transport and chemical transformation of reactive pollutants on an urban street using a computation fluid dynamics (CFD) model coupled with full photochemistry of reactive pollutants. An extensive comparison between simulated results and observations is conducted to evaluate the model, focusing on a field campaign occurred in Dongfeng Middle Street in Guangzhou, China. Observed CO and NO concentrations vary diurnally following traffic volumes. The model captures this observed diurnal variation and magnitudes of CO concentrations successfully. However, simulated NO concentration is three times higher than observation. This high bias is significantly reduced in the sensitivity simulation with lower NO x emissions. We find that oxidation products of O 3 photochemistry such as NO 2 and O 3 vary differently from primary pollutants, indicating important effects of photochemical reactions on their fates. The model appears to reproduce observed O 3 and NO 2 variability with time and altitude. Our analysis shows that high NO x concentrations in the urban street canyon may efficiently produce aerosol nitrate in the presence of NH 3 . Simulated inorganic NO 3 − aerosol concentration reaches up to 0.3 μg m −3 in July but increases an order of magnitude higher at lower temperature that favors partitioning of gas-phase HNO 3 to aerosol-phase, implying a serious concern for urban air quality in winter. ► We developed a coupled full chemistry-CFD model. ► The model was first applied to an observed case on an urban street canyon. ► The spatial pattern of secondary pollutants differs from the primary. ► Nitrate aerosol would be important for air quality on an urban street.