Abstract: To study the influence of heavy-duty vehicle characteristic parameters on CO₂ emission, the effects of rolling resistance coefficient, wind resistance coefficient, tire dynamic radius, accessory maximum total power, mechanical efficiency and torque loss of main retarder and gearbox on CO₂ emissions were calculated by VECTO software, taking Chinese van, European C2 truck under different operating conditions and European intercity bus as examples. The sensitivity of different parameters to the variation of CO₂ emission was analyzed. The results showed that the variation range of parameters such as rolling resistance coefficient, wind resistance coefficient, total accessories power, and torque loss in each gear of main retarder and gearbox had a positive linear correlation with the variation range of vehicle CO₂ specific emission. The variation of 20% of each parameter would cause a maximum variation of 4.4%, 7.2%, 1.9%, 1.2% and 1.4% of CO₂ specific emissions, respectively. The influence of tire dynamic radius on CO₂ was nonlinear. The change range of CO₂ emission caused by negative tire dynamic radius variation was higher than that caused by positive tire dynamic radius variation; the −20% tire dynamic radius change range would cause about 7.1% change range of CO₂ specific emission. There was a negative linear correlation between the variation of mechanical efficiency of each gear of the main retarder and gearbox and the variation of CO₂ specific emission, and the variation of CO₂ emission caused by the mechanical efficiency deviation of −2.8% was about 2.3%. The research results can provide a reference for carrying out the design of the energy-saving and carbon-reducing improvement of heavy-duty vehicles.