Abstract: In order to improve the process of gas metal arc welding, coated 316L stainless steel welding wires were developed by drawing and coating process. The coating composition included compounds of Ca and oxides of Na, Ti and Si. The two coated welding wires containing CaF₂ and CaCO₃ respectively were prepared. The surfacing stability of both welding wire without coating and coated welding wires was studied by electric signal acquisition system and high speed photography. The results show that the welding current of the welding wire without coating fluctuates greatly,the arc shape is unstable and the welding stability is poor. The arc of the coated welding wire with CaF₂ is unstable and the welding process is deteriorated. The welding stability of the coated welding wire with CaCO₃ is significantly improved compared with that of welding wire without coating, the current and voltage waveforms are very stable and the welding arc is in the shape of cone.