Multidisciplinary coupling among dynamics, tribology and elastic mechanics (strength and stiffness of shaft) on a shaft-bearing system with variable load, was studied in this paper. Special software (ADAMS and ANSYS) assisted with self-designed programs were applied to solve the problem. Dynamic responses of the shaft-bearing system were calculated on sine exciting force, and the relevant dynamic oil pressure distribution was obtained by solving Reynolds' equation according to the trajectories of shaft center. Dynamical stress on journal surface considering the dynamic oil pressure was calculated by the APDL (ANSYS parameter design language). Numerical results showed that dynamic stress distributing on the journey surface is related to the dynamic oil pressure and the variation of stress about time is determined by the dynamic response.