Abstract: Austenitic stainless steels with different grain sizes were electrolytically corroded by oxalic acid aqueous solution with a volume fraction of 10% and nitric acid aqueous solution with a volume fraction of 60%, and samples with twin and without twins were obtained. The grain size was rated by comparison method and cut-off point method, respectively. The results show that when there were twins, the results of the comparison method of coarse-grained samples were coarser than those of the cut-off point method, and the results of the cut-off point method were more accurate. The results of the comparison method of fine-grained samples were close to those of the cut-off point method, but both were finer. When there was no twin, the results of coarse grain sample comparison method were also coarser than those of cut-off point method. Because there was no twin effect in fine grained samples, the results of comparison method and cut-off point method were more accurate.