The invention relates to application of a PLC and an alternating current servo in a numerical control drilling and milling machine. A man-machine interface, a PLC, an X-axis servo driver, a Y-axis servo driver, a Z-axis servo driver, a main-axis frequency converter, an X axis, a Y axis, a Z axis, a main axis, an X-axis position detection cooling and alarm device, a Y-axis position detection cooling and alarm device, a Z-axis position detection cooling and alarm device and a main-axis position detection cooling and alarm device are arranged. The man-machine interface is connected with the PLC through a signal line. The PLC is connected with the X-axis servo driver, the Y-axis servo driver, the Z-axis servo driver and the main-axis frequency converter through signal lines. According to the application, the PLC is adopted, program parameters are altered and set and the operation state is displayed and monitored through the man-machine interface, and the content in the man-machine interface can be programmed; and the X-axis servo driver, the Y-axis servo driver, the Z-axis servo driver are all the fully-digital alternating current servo systems, an X-axis servo motor, a Y-axis servo motor, a Z-axis servo motor and a main-axis servo motor drive ball lead screws through couplings to move a workbench with a linear guide rail and a main-axis cutter head. By means of the application of the PLC and the alternating current servo in the numerical control drilling and milling machine, locating is precise, and the speed is high.