Abstract: The effect of applied longitudinal magnetic field on Fe5, Fe3 and Co-based plasma arc surfacing on low carbon steel was investigated.The influence of electromagnetic stir on the microstructures and properties of surfacing metal was discussed.And the impacts of magnetic density on the hardness and wear resistance of three alloys in surfacing metal had been systematically studied by using optical metallographic examination and macrohardness test.The results indicate that the proper magnetic parameters can refine the structure of deposited metal and improve its hardness and wear resistance.Moreover, it' s found that optimal magnetic parameter is constant in surfacing for different alloys.