Abstract: The thesis introduces how to calculate the static rigidity and the optimum distance between the bearings of a stepped main spindle by means of applicating finite element method. In the thesis, C1continuous interpolating function, of two nodes is selected to regard the deformation of the spindle as the superposition of the flexural deformation that is produced when the position of the bearing is in the case of zero displacement and the integral deformation of the spindle generatrix that is produced when the position of the bearing is in the case of assigned displacement, and the general solving method by electronic calculation is given that can calculate the optimum distance between the bearings when all kinds of loads are loaded to the stepped main spindle.