摘要：Factors for determining the spindle size are the shaft diameter,positions of bearing and motor,and entire length of the ***,it is important to find the assembling of the optimal design variables,which satisfy the stiffness and rotational speed required to the spindle.A general full factorial design method was used to verify some factors that affect the natural frequency of a *** is verified that the shorter shaft length and bearing span length represent the higher natural frequency,and there are some effects according to the change in the levels of *** detailed spindle dimension is determined by applying an EVD method,which can define the optimal bearing position through considering the limiting *** on the estimated regression model,the optimal spindle size and bearing distance that can improve the primary natural frequency are obtained,and the influence of design factors on the natural frequency is also analyzed.