In order to meet the demand of enterprises in the military electronics industry to improve the processing efficiency and precision for cavity structural parts, this paper puts forward an intelligent upgrading proposal of the CNC machining unit which is to conduct partial adaptive transformation of the existing CNC machine tools and to equip supporting systems such as industrial robot system, zero positioning system, accompanying fixtures, loading and unloading stations and master control system. The transformation practice shows that this proposal can realize the automatic identification of parts processing procedures, automatic collection of processing data and seamless integration with MES system. The time required for processing assistance (clamping) reduced by more than 60%, the effective utilization rate of equipment increased by more than 20%, and comprehensive processing accuracy increased from 0.15mm to 0.05mm.