The alien stone turning-milling compound machining center is a new generation gap multifunctional compound machining center. It is used to process rotating part of alien stone products and three-dimensional sculpture products. The pillar and guiding rail are the key parts of the machining center. The straightness error of the pillar and guide rail seriously impacts the linear motion precision of beam parts. Comparison the straightness of guiding rail with pillar or without pillar, it shows that the results meet the standard of GB/T16462-1996. So it ensures the accuracy of the linear motion precision of beam parts. It lays a solid foundation for achieving the design function and machining precision.