Simplified geometric model of the wheeled tractor- seat suspension system was constructed based on the software of Pro/E.The geometric model was then imported into ADAMS.The documentations of the tire property and road excitation were edited in ADAMS.The virtual prototype of tractor-seat-road system was established.The ride comfort of the tractor under different driving speeds and road excitations was simulated to explore the effects of speed and road excitation on the tractor riding comfort.The results show that the vehicle speed and road unevenness have huge impact on the ride comfort of tractor.The vertical vibration intensity of driver under the high driving speed is significantly higher than that under the lower driving speed.The subjective vibration sense of driver on the rough pavement is much stronger than that on the flat surface.The influence of the seat-suspension system on the riding performance was investigated.The results show that the seat-suspension system can significantly reduce the vibration amplitude of the vertical vibration and avoid the sensitive vibration frequency areas of the body’s internal organs and spine system.The riding performance was improved as well.