An automatic control system for the external thread whirling machine which is designed, with PLC as master controller and touch screen as human machine interface，using servo motor and AC motor as actuator, achieves automatic processing for different specifications pressing screw by setting different parameters. The control system can be a one-shot forming by thread whirling compared with traditional processing methods and does not require adjustment for master plate compared with the original external thread whirling machine, thus significantly reducing the operators skill requirements, eliminating human error makes knife angle more accurate.