Highprecision belt axes are mainly used in precision machinery machining, the overall performance of which directly affects the quality and precision machining. A highprecision belt axis used in vertical machining center was designed. By using the method of experimental verification and theoretical analysis with calculation, aimed at the design process for the belt axis, among which concerned with the appearance of size of spindle, type of bearing selection and combination method, mechanism of broacher to choose from and selection of seals devices were analyzed in detail with calculation and verification, and leave factory testing was completed. The testing proves that the overall performance of this belt axis meets the machining requirements of vertical machining centers, which can ensure the machining precision of the workpiece.