Abstract: Position of flux strip in its constricting arc is the key to constrain arc, which decides the heating characteristics of arc.In order to perfectly apply constricted arc by flux strips to ultranarrow gap welding, position of flux strip in its constricting arc has been analyzed by collecting voltagewaveform of flux strip which is as a probe.The results indicate the position of flux strip in its constricting arc and the transfer mode of melted flux strip can be estimated according to the numerical value of voltage waveforms of flux strip. When the distance from flux strip to the center of arc is increased, position of flux strip in arc zone will be changed, at the same time, the effect of arc heating flux strips and the contacting frequency of flux strip and droplets are reduced.In addition, the position of flux strip with different potential of flux strip was measured.