In order to improve the machining accuracy of a vertical machining center,a complete space error model of the vertical machining center was established based on the screw theory,and the space error compensation of the machine tool was realized.Based on screw theory,the forward kinematics solutions of tool motion chain and workpiece motion chain were deduced and established,the 21 geometric error principles of machine tool were analyzed,and the complete space error model of the vertical machining center was established based on the 21 geometric errors;the geometric errors identification was completed by using the nine line method;after solving the inverse kinematics solution of the machine tool based on the forward screw kinematics,the actual motion path of the motion axis was obtained,and the effects before and after compensation were compared by body diagonal experiment.The results show that the compensation effect of the proposed compensation method is significant,which verifies the accuracy of the machine tool spatial error model;by using the method,the machining accuracy of the machine tool can be improved.