Abstract: The inner contact stress and strain of a bearing change was found via developing a 3-D parameterized FEM model of bearings and a numerical simulation of the model with the software ANSYS. Then, the stochastic finite element method extended by Neumann (NSFEM) with Monte-Carlo method is introduced to consider comprehensively the effects of the original errors arising from manufacture and different working conditions including rotating speed and loads on the dynamic capability of bearing. With a stochastic virtual experiment done several times, the sensibilities to the reliabilities of all variable parameters of a bearing were given in form of probability, thus providing theoretically a reference for the fatigue strength calculation and optimum dynamic design of a bearing.