Abstract: Large-size CN forming gear milling is a king of high efficiency gear milling equipment, aiming at the machining of large-size gears by NC milling small-size turntable, a structure scheme of the faceplate on the turntable is proposed.Through the finite element modal analysis and experimental verification of the spindle box of CN gear milling machine and the faceplate assembly, the weak points and inherent characteristics of the structure are analyzed.To reduce the vibration in milling process, the structure of supporting oil cylinder for the faceplate is proposed.Through the time domain analysis, the necessity and feasibility of the faceplate support cylinder are verified, and the vibration state of spindle box in milling process is analyzed.The results show that the vibration amplitude of milling cut-in section and cut-out section is large, and the feasibility of the proposed scheme for the structure of the faceplate support oil cylinder is confirmed, which provides guidance for milling processing, and can provide theoretical support for the structural design and optimization of machine tools.