Abstract: In order to study the vehicle ride comfort under the characteristic of coupling vibration between vehicle and pavement ,a full‐car model was built by using software CarSim .Road grade A~D defined in GB7031 were also simu‐lated and verified numerically by using inverse Fourier transform .The acceleration rates and coefficient of tire radial dy‐namic forces under different speeds and road grades were computed .The simulation results indicate that 1) vehicle acceler‐ation rates significantly increased with decrease of road grades and increase of vehicle speed .The acceleration rate changed from 0 .259 9 m/s2 at the speed of 50 km/h on grade A road to 1 .688 9 m/s2 at the speed of 120 km/h on grade D road , which increased approximately 5 .5 times .Vehicle ride performance becomes worse .2) The effect of road roughness and vehicle speed on the dynamic force was significant .The dynamic force coefficient (DFC) produced by vehicle changed from 0 .083 3 at the speed of 50 km/h on grade A road ,to 0 .775 4 at the speed of 120 km/h on grade D road ,an increase of around 8 .3 times .The lower the road grade and the higher the vehicle speed ,the greater the dynamic force coefficient which will cause more serious damaging effects on the road .