The effect of different dosages (0.0,3.5,6.5 Gy) of X-ray on histological structure and expression of c-Fos and KGF in skin of developing Mouse( Mus musculus )(1 d,5 d,10 d,20 d) were investigated. Results showed that skin structure was not obviously changed after 1 d irradiation; thickness of epidermis,dermis,hypodermis and number of hair decreased,and serious fibrosis appeared in skin of developing Mouse after 5 d irradiation;fibrosis reduced,dermis dense connective tissue and hypodermis recovered gradually after 10 d irradiation with 3.5 Gy of X-ray,while histological structure recovered slowly after irradiation with 6.5 Gy of X-ray. The histological structure of skin recovered after 20 d irradiation with 3.5 Gy of X-ray,while all individuals died after 20 d irradiation with 6.5 Gy of X-ray. The skin of developing Mouse exhibited c-Fos and KGF immunoactivity,and the expression of c-Fos and KGF in radiation groups was obviously increased than that of control groups. The greater dosage was used,the stronger expression of c-Fos and KGF was observed. The expression of c-Fos decreased gradually,while the expression of KGF displayed wave pattern after irradiation with 3.5 or 6.5 Gy of X-ray. There was a trend that histological structure and expression of c-Fos and KGF recovered slowly to the normal state after irradiation. The results indicate that high dosages irradiation causes serious damage to the skin of developing Mouse as well as cell apoptosis and necrosis. After irradiation,the body possess self-healing function,and the number of cells in skin increases obviously, and histological structure of skin recovers gradually.