<p>A novel method, energy method, for solving bearing stiffness in rotor system supported by multiple bearings is proposed. Energy method has no restrictions on bearing type, bearing arrangement, bearing number and load type in rotor bearing system and can significantly simplify the solution procedures involved in determining bearing displacements and bearing stiffness. The potential energy model of flexible rotor bearing system is derived by combining finite element method and bearing load–displacement relationship and can be expressed as the function of rotor shaft nodes’ displacements. Based on the principle of minimum potential energy, the true displacements of all nodes in the system are calculated by optimization algorithm, and then the stiffness for each bearing is obtained. The effectiveness of the proposed energy method is verified by comparing with the results of bearing displacements, loads and stiffness coefficients in published literatures. Based on the proposed energy method, the effects of the rotor shaft flexibility, bearing arrangement, load position, bearing radial clearance and initial angular misalignment of outer ring caused by installation error on bearing stiffness in the rotor bearing system are investigated.</p>