The influence of the cutting force and the frictional thermal coupling deformation is rarely considered simultaneously when conducting tolerance modeling of machine tool spindles,resulting in a great difference between the tolerance model and the engineering practice,and it is difficult to guarantee the machining accuracy of machine tool spindle.Therefore,a tolerance modeling method of machine tool spindle based on thermal coupling deformation was studied.According to the actual working condition of machine tool spindle,the Jacobian-Torsor tolerance model of original geometric error of spindle was established by using small displacement screw theory to express the geometric change of feature;the Jacobian-Torsor tolerance model was modified according to geometric variation,and the tolerance variation representation model of typical fit features was added;the deformation of the spindle under the coupling of cutting force and friction heat was calculated by using ANSYS;the results were introduced into the modified Jacobian-Torsor model to obtain the tolerance model of machine tool spindle under thermal mechanical coupling deformation.The results show that the translation of the assembly clearance between the spindle and the bearing in the radial y direction is reduced by 0.009 mm,the rotation along the radial direction is reduced by 0.000 8 mm,the interference is increased,the wear of the spindle is accelerated,and the rotation accuracy of the spindle is affected.The designed model can provide reference for tolerance design of machine tool spindle,and the performance of spindle can be predicted and improved by using the model.