Abstract: Longitudinal magnetic field was applied on plasma arc surfacing Co-based and Ni-based alloys.Hardness, wearing and microstructures of the two ceramics composite surfacing deposit were tested in this paper.The surfacing deposit of introducing the longitudinnal magnetic field shows higher properties than the surfacing deposit without magnetic field.The properties of surfacing deposit are optimal when surfacing current is 160A and magnetic field current is 3A for Co-based alloy, the effect of grain refining for surfacing microstructure is most obvious at this time;the optimal surfacing and magnetic field currents for Ni-based alloy are 160A and 3A, and the number of hexagon ceramics hard phases of Cr₇C₃ section is most and evenly distributed.It shows that the longitudinal parallel direction of hard phases are consistent, so the hardness and wearing resistance are best.With the increasing of magnetic field current, the properties of surfacing deposit declined because electromagnetic damping play a doninant role.