Abstract: Under the condition of short circuit transition of CO₂ shielded welding or metal active-gas welding,current and voltage signals always change frequently.It is difficult to estimate the torch offset by the transient signals when the torch swings,so the swinging currents of two sides were discretely integrated and the two integral were compared to recognize position error signal of torch.The problem of centering of torch can be efficiently solved.As there are many factors which can influence the difference of integrals and the regularity of influence is complex,it is difficult to establish an ideal mathematic model of control.The self-adaptive fuzzy control method was used.The developed seasor can achieve good effect in tracing control.