Abstract: Activating flux was used in laser arc hybrid welding to improve the penetration. A thin layer of activating flux was brushed on the surface of base metal to be welded, then laser arc hybrid welding was employed to cover the layer. The influence of welding parameters on the weld formation, microstructure and properties were studied. The results show that the penetration of laser arc hybrid welding was increased and its width was reduced by activating flux. Finer microstructure can be acquired in the activating laser arc hybrid welded joints. The trend of micro-hardness distribution was basically the same whether the workpiece was brushed activating flux or not. The tensile strength of activating laser arc hybrid welded joint reached 92% of base metal, and the toughness of welded joint was good. The corrosive speed of activating laser arc hybrid welded joint was lower than that in laser arc hybrid welded joint without activating flux.