An equivalent simulation and analysis method for the bearing misalignment of an engine rotor based on multi-body transient contact dynamics was proposed.The multi-body dynamic model of the high-pressure rotor-bearing-partial support structure was developed.The transient contact forces and moments between a single roller and the outer ring, between all rollers and the outer ring, as well as between the outer ring and the support structure were analyzed considering the non-linearity of contact and the flexibility of support structure.The vibration response of the support structure was studied and the generation mechanism and transmission of bearing misalignment fault were investigated.The results show that the complex interactions, caused by the variation of the relative position of the single roller to the rings and also by the rollers locating in compacting or loosening regions, are the direct reason of the appearance of complex frequency components in the contact force.The misalignment excitations are from the transient resultant contact force and torque between all the balls and the outer ring.Harmonic frequency components of axial vibration are the typical characteristics of misalignment faults and the magnitudes of the double and triple harmonics of the axial and radial vibration can represent the severity.The results provide reference for the diagnosis of misalignment in gas turbines.