Abstract: Because constricted arc has many merits, such as high energy density and high velocity of plasma, it is applied in many welding fields.The characteristics of constricting arc with flux strips was studied by sending two pieces of flux strips into arc along both sides of the arc.The results show that flux strips are melted by heating of arc column under a stable welding condition, and certain action length of flux strips that act on the arc are formed on both sides of the arc, and the length will increase with the decrease of voltage and the increase of velocity of feeding flux strips.Action length can directly influence on the morphology of constricting arc with flux strips, and with action length increase, arc width will shorten and arc length will elongate, as a result the welds become deep and narrow;when the distance from the center of the arc to the flux strip is reduced, arc width will distinctly become narrow, and weld depth will become deep and weld width will become narrow; ultra-narrow gap welding can be achieved by use of the characteristics of constricting arc with flux strips.