In order to solve the problem of incomplete modeling of spatial positioning accuracy of NC machine tools and the residual error of traditional reverse superposition compensation,a spatial positioning accuracy analysis and compensation technology for horizontal machining center was proposed.Taking a horizontal machining center as the research object,based on the spinor theory and the analysis of the machine tool motion chain,two forward kinematics solutions of the horizontal machining center motion chain were deduced and calculated,and the spatial positioning accuracy model of the horizontal machining center was constructed based on the analysis of 21 geometric errors;21 geometric errors were identified by using the twelve line method,and the discrete diagram of spatial positioning accuracy prediction of the machine tool was output;then,the accuracy of the spatial positioning accuracy model of the horizontal machining center was verified based on the spatial diagonal test;finally,the spatial positioning accuracy compensation was realized based on NC code optimization compensation technology.The results show that the maximum relative deviation between the predicted value of the spatial positioning accuracy model and the actual average value is no more than 2 μm,the highest compensation efficiency of NC code optimization compensation technology is 88.75%.