The microstructure and microhardness of plasma welding (PAW) joint with surfacing welded cobalt-based alloy have been investigated by using Optical microscope (OP) ,X-ray, scanning electron microscope (SEM),and microhardness testing. The results show that the surfacing layer microstructure is made up of the dendrite (γ-Co) and eutectic (γ-Co+M7C3). The microhardness decreases from surfacing layer to substrate. The highest hardness on the surfacing layer obtains with 550HV up. The fusion zone’s and substrate’s microhardness is about 380HVand 280HV respectively.