Abstract: Current-carrying arc erosion tests of W/Cu current-carrying frictional pairs were carried out by the home-made current-carrying arc tester. The arc erosion behavior and arc erosion mechanism were studied. The results show that with the arcing time increasing, the current of current-carrying arc decreased, the voltage increased, and the electric field intensity first increased then decreased. The current-carrying arc was divided into three stages of ignition, stable burning and extinction. The time intervals of the three stages were about 7%,89% and 4% of the total arcing time. The serious arc erosion of copper specimen occurred at the ignition stage and at the beginning of stable burning stage. With the increase of test current, the existence time interval of the arc in metallic vapour state extended; the width of arc erosion pit on copper specimen surface increased and the depth first increased then decreased. The results were related to the increasing deposition of tungsten with high melting point.