Abstract: According to the theory of components reliability sensitivity, the reliability-based sensitivity of radial journal bearings under the hydrodynamic lubrication are analyzed, in which some analysis about the correlation between the various parameters are carried out. Without losing the accuracy, the process of the calculation is substantially increased in efficiency by simplifying of the theoretical model, and finally the numerical simulation results are given to test the theoretical derivation. All of the analysis provides some theoretical basis for the selecting and using the hydrodynamic radial journal bearings and the stiffness design of whole shaft system in the engineering practice.