Objective To study the impact of aging on the capability of lung stem cell steady-state maintaining and bronchial epithelial cells regeneration and differentiation during the repair of lung epithelial cells after naphthalene induced bronchial epithelialium injury.Methods The proportion of lung stem cells in mice after naphthalene treatment was analyzed by immunohistochemistry and FACS.The repair efficiency of lung epithelial cell in young and old mice was examined by immunohistochemistry staining and FACS.Results The data suggested that aging didn ’ t change the proportion of lung stem cells ( including the distal lung epithelial stem cells/progenitor cells and lung mesenchymal stem cells/progenitor cells) under normal physiological conditions.After naphthalene injury, more serious injury and decreased repairing capacity was observed in old group.Lung progenitor cells /total lung cells decreased during the repair process of lung bronchial epithelialium ( clara cell) injury.The ratio of regenerated cell to lung progenitor and stem cells were also significantly decreased in old group.Conclusion The regenerated capability of lung stem cells after lung bronchial epithelialium injury decreased with aging.This might be the reason of more incidence of lung injury and worse therapeutic results in the elder in clinic.