A high-Mn-N low-Ni superduplex stainless steel 25Cr-2Ni-3Mo-10Mn-0.5N with multi-scale microstructures has been prepared through severe cold rolling and annealing, and the effects of multi-scale grains on the pitting corrosion and mechanical properties have been investigated. The results show that the multi-scale microstructures have a strong relation with the annealing time, that is, the average grain sizes of austenite and ferrite increase with prolonging of the annealing time at 1050 oC, they have the minimum values of 1.5 and 7.18 μm, respectively, when the alloy is annealed for 1 min. The tensile strength, yield strength and reduction in area of the sample decrease with the growth of multi-scale grains, whereas the pitting corrosion resistance of the specimen is enhanced. The multi-scale microstructures play an important role on the pitting corrosion and the mechanical properties of superduplex stainless steel 25Cr-2Ni-3Mo-10Mn-0.5N.