A rat model of rediation-combined wound healing was used,and routine light microscopy observation,electron microscopy observation, immuno histochemistry,and in situ hybridization were performed to study MMP1 and TIMP1 expression during the healing process. The wound healing process was impaired and delayed. After irradiation for rats receiving 25Gy Gamma ray locally the irradiated wounds healed 6 days later than non — irradiated controls. The folfowing changes of MMP1 and TIMP1 expression were found: （1） In the early inflammatory phase and in the period of granulation tissue formation,MMP1 expression was only slight,if affected at all in the newly formed epidermis of irradiated wounds. Later,the epidermal expression of MMP1 in radiation wounds was comparatively increased following the delay of the heallng process. From the 3rd day to 14th day after wounding, TIMP1 was weakly positive in the proliferating keratinocytes of control wounds and became negative after epidermal covering, whereas no or only slight epiderma expression was detected in the irradiated wounds before epidermal covering. （2） Compared to controls,MMP1 and TIMP1 expression in irradiated wounds was markedly decreased in fibroblasts,endotheliocytes and macrophages. The expression phase was prolonged due to the delay of the healing process. We conclude that the reduced expression of MMP1 and TIMP1 in granulation tissue of irradiated wounds retards such important processes as cell migration and angiogenesis, and thus slow the healing process. The expression of MMP1 in the newly-formed epidermis may help the process of reepithelialization; but in the late healing period, overexpression of MMP1 and decreased expression of TIMP 1 in the epidermis may hinder the establishment of basal membrane and scar formation.