A considerable researches have been conducted to provide rather compelling evidence that the grain size and grain boundary distribution possess much influential effect on mechanical properties and corrosion behaviors in most metals and alloys. However, the effects of grain size and grain boundary distribution on anti-corrosion ability of materials have been independently studied. Some investigations indicate that the occurrence frequency and distribution characteristic of twin-related (especially Σ3ⁿ coincidence site lattice (CSL)) grain boundaries play a particularly important role in optimization of grain boundary character distribution. Unfortunately, both of these factors are interactive in annealing processes and there is a need to identify the independent role of the factors in anti-corrosion ability. In this work, a high manganese austenitic twinning-induced plasticity (TWIP) steel was used as experimental material and the anti-corrosion behavior of this steel resulted from both the grain size and grain boundary distribution was studied. The cold-rolled high manganese austenitic TWIP steel sheet was annealed at 700~1000 ℃ for 10~30 min to obtain microstructure with various grain sizes and CSL grain boundaries. The average grain size and grain boundary distribution characteristics for all the annealed steel sheets were obtained by the online analysis of EBSD data with HKL-Channel software. The anodic polarization curves were measured using CorrTest4 electrochemical workstation in 3.5%NaCl solution at 25 ℃ with a scan rate of 0.5 mV/s. The results show that both of the grain size and the occurrence frequency of CSL grain boundary caused by the uniformity of recrystallized microstructure have much effect on the anti-corrosion ability of this high manganese TWIP steel. When the recrystallization process just finished, and grains were inhomogeneous and not start to grow, the average grain size has a great influence on anti-corrosion ability. With increasing the grain size, the anti-corrosion ability of this high manganese TWIP steel was weakened. When the recrystallized grain growth fully takes place, the occurrence frequency of CSL grain boundary has the dominant effect on the anti-corrosion ability. The anti-corrosion ability was optimized with increasing the frequency of CSL grain boundary.