Abstract: To study the change of the concentrations of NO₂ emitted by motor vehicles on the urban road, 4 roads in Dadukou District, Chongqing Municipality were selected for one-week automatic online monitoring. Combined with the information of traffic flow and vehicles collected by RFID Base Stations on the road, the change features of NO₂ concentration and traffic flow, as well as their correlation were analyzed. The results showed that the daily averaged concentration of NO₂ on 4 roads was 29-57 μg/m³, all lower than Level 2 standard threshold of Ambient Air Quality Standard (GB 3095-2012). The hourly concentration of NO₂ peak value at about 20:00 was significantly higher than that at 08:00, with the minimum value appearing at around 14:00. The traffic flow of 4 roads had the obvious trend of morning and evening rush hours. The traffic flow at weekends was 20%-40% lower than the average traffic flow on workdays. The vehicle models with a high proportion included minibus, taxi, bus, and light truck. The change of the hourly concentration of NO₂ was consistent with that of traffic flow. Both of them had the obvious trend of morning and evening rush hours, but during the evening rush hours, the peak concentration of NO₂ appeared slightly later than the peak value of traffic flow.