An identification method of modal parameters of computer number numerical control (CNC) machine tool based on selfexcitation is proposed. Experimental modal analysis of XHK5140 machine tool was completed using by this method. The first four grades of modal parameters of the machine tool were identified. Which results were finally compared with that of other computer modal analysis, and the validity of the method was verified. The difficult problem of traditional modal experiment equipment to excite CNC machine tools is solved.