P>Objective To explore the functional role of Id2 in skeletal muscle regeneration. Methods Id2 expression vectors were transferred into C2C12 cells. The transferred and un-transferred C2C12 skeletal muscle cells were exposed to 50μmol/L H2O2 and 2% horse serum for 12 hours without fetal bovine serum(FBS). Expression of Id2 gene in transferred and untransferred C2C12 cells was observed by RT-PCR. Expression of various myogenesis related proteins in the transferred and untransferred C2C12 cells were observed by Western blotting. Expression of Id2 and AIF proteins in the normal, fiber-damaged and denervated skeletal muscles were observed by immunofluorescence.Results Compared with un-transferred cells, the Id2 transferred cells exhibited higher differentiation. Immunofluorescence staining revealed that 50μmol/L H2O2 treatment increased the expression of nucleic Id2.Under the oxidative stress, Id2 repressed both MyoD repressors and myogenin activator. Two percents of the horse serum, which usually was used to induce myoblasts differentiation, caused most of Id2 proteins translocation from nucleus to cytoplasm. Translocation of Id2 protein from nucleus to cytoplasm inhibited the ROS-induced expression of mitochondrial apoptosis inducing factor(AIF). Immunofluorescence analysis implied that the denervated skeletal muscle showed more increased Id2 and AIF proteins in the nucleus.Conclusion Id2 translocation from nucleus to cytoplasm can accelerate differentiation of skeletal muscle cells. The functional role of Id2 during the skeletal muscle regene