The stiffness of the frame has a great influence on the ride comfort of the heavy truck. Reducing frame thickness was proved to be unacceptable in terms of ride comfort, which is verified by the testing results. The truck frame was reinforced in order to improve the ride comfort. The modal analysis showed that the pitch frequency of the vehicle has increased 0.5 Hz and the frequency response has decreased by 20%. In order to research the influence of frame stiffness on the heavy truck ride comfort, a detailed model including a flex frame, chassis suspension, cab suspension, driveline, etc., was built by MSC.ADAMS. The Simulation results showed that the ride comfort can be improved by reinforce the frame, and the ride comfort can be improved by 5%∼10%. The results of this study need to be further examined through field testing.