Abstract: In this paper, the static stiffness of the spindle is analyzed and studied through three methods: theoretical calculation of the spindle static stiffness, finite element analysis of the spindle on the workbench, and physical test verification on the experimental bench. Comparing the values and error rates of the static stiffness obtained by the three methods, basically the static stiffness value of the spindle can be calculated correctly. It provides an accurate method for calculation and analysis of the static stiffness of the spindle, and provides a theoretical basis for the performance index and application of the spindle. According to the calculation formula, the influence of the main shaft front overhang, the main shaft bearing span and the main shaft bearing preload on the static stiffness of the main shaft is theoretically analyzed; meanwhile, how the three influencing factors should be balanced and comprehensively applied in the spindle structure design is also systematically analyzed. The comparative analysis on the three influencing factors affecting the static stiffness of the main shaft are compared and analyzed, which provides a theoretical basis for design of the spindle.