Aiming at the problem that the spatial error model of machine tool is not complete and the traditional sensitivity analysis has limitations,which leads to the inaccurate traceability for key geometric error and the difficulty of quantitative verification of key geometric error judgment results,a method of judgment and quantitative verification of key geometric error of machine tool was proposed by taking a vertical machining center as the research object.Based on the spinor theory,the spatial error modeling of the vertical machining center was studied,and the complete spatial error model of the machine tool was output;on this basis,based on the traditional local sensitivity analysis,the key geometric errors of the machine tool were determined by using the error contribution factor;the judgment results were verified by numerical simulation experiments.The results show that compared with the traditional sensitivity analysis results,it is more accurate to determine the key geometric errors by using error contribution factor;the results based on the error contribution factor can not only quantify the influence degree of geometric error on machine tool spatial error,but also provide theoretical reference for machine tool component manufacturing accuracy design.