In order to study the road emission characteristics of national Ⅵ natural gas heavy-duty vehicle, the portable emission test system (PEMS) was used to carry out the actual road emission test of national Ⅵ natural gas heavy-duty semi-trailer tractor , and the relationship between pollutant emission factors and vehicle driving parameters was analyzed. The results show that due to the poor driving conditions in the urban area and frequent acceleration and deceleration, the two dynamic parameters are the highest. The driving conditions of the suburban expressway section are better, and the dynamic parameters are low.and the emission factors of CO, CO₂, NO_x and THC are the highest in the urban area and the lowest in the suburbs, which are positively correlated with the dynamic parameters. With the increase of vehicle speed, pollutant emissions gradually decreased, and the decline was relatively rapid at low and medium speeds. As the vehicle speed increased from 0~10 km/h to 10~20 km/h, and the emission factors of CO, CO₂, NO_x, and THC decreased by 25%, 69%, 43%, and 60% respectively; With the increase of acceleration, the pollutant emission gradually decreased, the emission factors are highest in the low-speed and high-acceleration range(v≤30 km/h, a≥0.8 m/s² ). It is recommended that the driver should avoid driving at low speed and high acceleration when driving this type of vehicle to reduce vehicle emissions. At the same time, the emission rates as well as the emission factors exhibited a strong positive correlation with the vehicle specific power (VSP). As a function of vehicle speed acceleration and road grade, VSP can quantify the emissions of China Ⅵ natural gas heavy vehicles, and thus model bus emission under the different driving conditions.