Abstract: In order to study the force on tire of wheeled tractor on typical road conditions, a simulation model of wheeled tractor was built using the multi-body dynamics software RecurDyn. The model consisted of four wheels, fore and rear axles, and a body frame, and the axles were imposed on certain load appropriately. An interaction model between tires and soft soil was established using the Fiala tire module of RecurDyn. The simulations of displacement and force of the tires were conducted on 20° upslope, 44° ultimate upslope, 20° downslope and 34° ultimate downslope roads respectively. The tire force that the wheeled tractor run over a cylindrical obstacle was analyzed under two different speeds. Results showed that the difference of the impact forces applied on the front wheel was obvious on different slope roads. The maximum impact force of the front wheel on 44°upslope was 67.73% higher than that on 20°upslope. The maximum impact force of the front wheel on 34°downslope decreased by 8% compared with that on 20° downslope. The maximum force of the front wheel decreased by 16.13% when the wheeled tractor over a cylindrical obstacle with the speeds decreasing from 1.356 m/s to 0.678 m/s. The analysis results provided references for the study on the tire force of wheeled tractor.