Abstract: The effect of the zinc coating on the arc heating behavior was studied by the arc shape visual sensing system and voltage and current collecting system.The results show that the zinc coating can stabilize the arc as the plasma cathode during welding with lower current, but with the rise of the welding current the zinc coating will vaporize acutely, which make the arc edge ascend, and the contact area between the arc and the workpiece is lessened to reduce the heat input, which reduces the thickness of the interfacial brittle compounds.