Abstract: The relationship between armature induced voltage and wire-feeding motor speed in the limited unipolar mode of reversible pulse-width modulation(PWM) speed-control system is analyzed,and a reversible PWM speed-control system based on the digital control of a digital signal processor(DSP) is designed.The control method can eliminate the effect of load current on the speed of the wire-feeding motor by using synchronous sampling of armature voltage at the moment of zero current.The digital PI regulation method is used for adjusting the PWM duty-cycle to keep the armature induced voltage constant and improve the stability of wire-feeding.The test results show that the rate varieties of wire-feeding under the conditions of variable power network voltage and change of wire-feeding tube from straight state to a cycle of φ400 mm at the middle all meet the standard requirements.