Objective To explore the expression of myogenic regulatory factors MyoD and myogenin in DMD mouse model mdx mice at different age.Methods The gastrocnemius muscles of mdx and normal C57 mice at different age were collected and cut into frozen sections and stained by H.E.Pathologic changes of the muscles were examined by light microscopy.The expression of myogenic regulatory factors MyoD and myogenin were detected by SABC-DAB staining.Results The degree of muscle degeneration and regeneration was different in mdx mice at different ages.The expression of MyoD and myogenin was strongest in 1 month old mdx mice.The expression of MyoD and myogenin could be ever detected in 13 months old mdx mice and couldn't be detected in normal C57 mice at the same age.Conclusions MyoD and myogenin play a role in muscle regeneration after muscle injury.They can be used as an index to identify muscle precursor cells and reflect muscle regeneration.