Coupling simulating modal between dynamics and tribology was built for a flexible crankshaft-bearing system of an internal combustion engine considering misalignment caused by elastic deflection of the crankshaft. Coupling analysis has been done in the rating condition by the software ADAMS and Matlab. Coupling relation among dynamical performance of the crankshaft, tribological behaviors of the 5 main bearings and misalignment of crankshaft journal has been investigated in detail. It showed that the maximum pressure of oil film for the main bearings increased obviously and the minimum thickness of oil film decreased greatly when the journal misalignment was taken into consideration. Some changes were also taken place simultaneously for the dynamic responses of the system.