In order to improve the pitting corrosion resis tance of steel, a surfacing layer of Mn-N duplex stainless steel was prepared on Q235 steel plate by plasma build-up welding.The horizontal microscope was used to observe the microstructures of the solution-treated surfacing layer, and the distribution of each alloy element was analyzed by scanning electron microscope equipped with EDS. The pitting corrosion resistance of Mn-N duplex stainless steel plasma surfacing layer after treated at different solution temperatures was measured by ferric chloride immersion experiment and Electrochemical Impedance Spectroscopy（EIS）. The results show that, with the increase of the solution temperature, the pitting corrosion resistance of ferrite decreases, while the pitting corrosion resistance of ferrite austenite increases and the pitting corrosion resistance of the surfacing layer shows a trend of increasing in advance and then decreasing.After treated at 1 230 ℃, the surfacing layer has the lowest pitting corrosion rate of 0.017 6 g/h. EIS test shows that the surfacing layer after solution treatment at 1 230 ℃ has the highest resistance to pitting corrosion. The alloy elements redistributed in the two phases during the solution treatment may be the dominant factor for the differences in the pitting corrosion resistance of the surfacing layer after treated at different solution temperatures.