To realize type selection and optimum configuration of grading functional units for numerical control(NC) machine tools,a modular configuration design method for NC machine tools based on multi-domain mutual-use(MDMU) is put forward.The modules are defined by mechanical-electrical-hydraulic characteristics pool of the functional units of the machine tools.The product partial order templates are constructed by the membership and gradation relations of the modules.The key module,related module,virtual module are defined to represent the priority and significance of various modules.The instantiation rules of the modules are defined by type selection and optimum configuration constraints of components and parts.The correlation between two modules is reckoned by fuzzy membership of comparable characteristics.The key modules are selected by Karhunen-Loeve transformation.The product tree is reconstructed by multi-class support vector machine(SVM).The module instantiation is enhanced by design.The mutual-use of parts which are difficult to be reused directly is realized by part structure variation.The modular configuration design based on MDMU is finally accomplished by getting modular bill of material(MBOM) and assembly from the design requirements.The modular configuration design prototype is developed and applied to the design of the HMS series horizontal machining center.The test results proves that the current design of NC machine tools is extended to layout domain-adapting domain-part variation domain MDMU modular configuration design by characteristics-modules-templates hierarchy mapping,so it expands the mutual-use scope,decreases the ratio of non-standard parts between the product families with different layouts.It helps to improve efficiency and quality of NC machine tools design.