Abstract: The voltage negative feedback system with the current positive feedback system is analyzed, and the equivalent efficiency condition is derived that the velocity negative feedback system is the same as the voltage negative feedback system with the current positive feedback system. A wire feeding system based on TL494 which is used in CO₂ arc welding machine is designed. Because pulse width modulation technology is used in the system, the motor driven by IRF9530 in the system can run smoothly at adjustable velocity. The system can be protected if current is overloaded. The system stability is tested and the variation ratio of velocity is lower than 5% when the load changes from 25N to 50N and source voltage from 342V to 418V. Under proper conditions, the variation ratio of velocity may be zero.