The invention discloses a duplex stainless steel plasma anode nitriding surface strengthening technology. The duplex stainless steel plasma anode nitriding surface strengthening technology comprises the following steps that (1) duplex stainless steel surface pretreatment is carried out; (2) plasma auxiliary anode nitriding is carried out, wherein a plasma auxiliary anode nitriding technology is adopted for conducting surface modification and strengthening processing on ultra-low carbon duplex stainless steel discs, and duplex stainless steel obtained after surface pretreatment is placed into an anode nitriding device for nitriding treatment; and (3) annealing is carried out. By means of the duplex stainless steel plasma anode nitriding surface strengthening technology, formation of a brittle phase can be effectively restrained, the discs have the excellent toughness matching from the surface layers to the center parts, workpiece secondary deformation caused by temperature gradient is reduced as many as possible on the basis of guaranteeing the excellent texture uniformity and mechanical property, coarsening damage caused by arc striking, edge effects and the like on treated surfaces can be avoided, meanwhile, formation of the white and bright semi-stable state compound S phase is better achieved, separation of brittle phases such as epsilon-Fe2-3N and gamma'-Fe4N is restrained,and the discs have the higher hardness, abrasion resistance and erosion resistance.