The paper aims to improve the hardness and wear resistance of F51 duplex stainless steel. The F51 duplex stainless steel was nitrided at 450 ℃ and 550 ℃. The microstructure of the nitrided layer of F51 duplex stainless steel was observed by optical microscopy (OM) and scanning electron microscopy (SEM). The phase composition change of the nitrided layer in different depth was measured by X-ray diffraction (XRD). The microhardness and the wear resistance were evaluated by microhardness tester and friction wear tester respectively. The surface wear tracks were observed by laser scanning confocal microscope (LSCM). The low-temperature nitrided layer of F51 duplex stainless steel was mainly composed of phase γN and the phase distribution from the surface to the inner was γN→γN+aN (little). The high-temperature nitrided layer was mainly composed of phases CrN + aN, the phase distribution from surface to the inner was CrN+aN→aN+γN. The high-temperature nitrided layer was 3 times thicker than the low-temperature nitrided layer. The average surface hardness of the low-temperature nitrided sample was 3.5 times as high as the untreated sample; while the average surface hardness of the high-temperature nitrided sample was 4 times as high as the untreated sample. The friction coefficient of untreated sample was 0.71. While the friction coefficients of low-temperature and high-temperature nitrided layers were greatly reduced, which were 0.24 and 0.17, respectively. The width and the depth of surface wear tracks of the nitrided samples were reduced obviously compared with the untreated sample. The low-temperature nitrided layer of F51 duplex stainless steel mainly consists of phase gN, and the high-temperature nitrided layer mainly consists of phases CrN+aN. Both hardness and wear resistance of nitrided samples are effectively improved.