Abstract: The constitute of motor vehicles and the development trends,the relationship of vehicle flow and nitrogen oxides,and the contribution rate of exhaust from every kind of motor vehicles in Guangzhou were analyzed. The results showed that light-duty vehicles (including taxis) and motorcycles are main emission sources of carbon monoxide and hydrocarbon while heavy-duty vehicles including buses are among main emission sources of nitrogen oxides. The focus of controlling vehicle emission in Guangzhou was proposed to be the control of emissions from motorcycles,light-duty vehicles (especially saloon cars including taxis)and buses.