The ASM emission test system is suitable for emission testing of gasoline vehicles with ignition engines, gaseous fuels such as natural gas and LPG, or dual-purpose fuel vehicles. The system consists of chassis dynamometer, five-gas analyzer, cooling device, driver assistant, safety inhibiting device, inertia simulator, engine tachometer, environment station and computer control system. The test was divided into two constant velocity conditions: ASM5025 and ASM2540. Chassis dynamometer is used to simulate the driving load of the vehicle on the road. Thus, the concentrations of various pollutants CO, CO2, HC and NOX discharged by the vehicle under a certain road load are tested.