Ammonia(NH3) generated from vehicles which is an important source of atmospheric PM2.5 can react with the acidic gases in the atmosphere to produce ammonium salt. To understand the emission of atmospheric NH3 in the traffic environment of Beijing City, China, and find the factors which affect the NH3 concentration of traffic environment and relationship between them, NH3 concentration at two observation sites was collected during the seven-month observatory experiment using DOAS instrument. One observation site was located in a typical traffic environment close to the eastern gate of Beihang University (BH), the other one was located on the top of the seven-floor building in a typical downtown environment (BMEMC). The analytical result showed that the emission of pollutants is generally low in summer and high in spring and autumn and the 24 h NH3 concentration at the BH site (25.19 μg /m3) was higher than that at the BMEMC site (15.90 μg /m3). The change trend of concentration in whole day is stable, and there are obvious peaks and troughs, which indicates that the contribution of traffic pollution sources to NH3 is stable. The correlation analysis indicated that NH3 concentration was well correlated with the concentrations of PM2.5, NO2, NOx and CO, but only weakly correlated with the concentrations of NO. It is concluded that the wind above Grade 3 is beneficial to the rapid diffusion and reduction of ammonia concentration. After calculating the yearly emissions and hourly emissions of all types of motor vehicles in Xueyuan Road, the result shows that NH3 mainly comes from small passenger cars (gasoline) and taxis (gasoline) (97.9%).