In order to improve the efficiency and automation level of NC machine tools, this paper puts forward the PLC hole control scheme after analyzing common servo control systems. On the basis of defining motor specifications, the NC electrical control system of machine tools is designed. The output and input modules of the system are defined by the PLC device. The parameters of the input and output signals are clearly defined, and the accuracy of the machine tools is tested and modified. It is found that after the modification, automatic loading and unloading processes are completed, and the processing time is reduced by nearly 30%. The time of changing and moving the tool is reduced by about 28%. At the same time, the accuracy of tool moving is improved. Thus, the automation of NC machine tools based on PLC reduces the down time, the labor input, and achieves the technical targets of production.