Abstract: To study the age-dependent variation of superoxide dismutse(SOD) activity and malonaldehyde(MDA) contents in Drosophila melanogaster and the correlationship between the variation and life-span.The numbers of living and died flies were recorded daily.Flies of different ages(days)were homogenated separately.The examining the SOD activity and MDA contents in the homogenates have been made.Ages of Drosophila being younger than 40、50 days,the SOD activity increased with advancing age,while that decreased in aged Drosophila.The levels of MDA increased significantly with aging.The SOD activity of male flies is significanthigher than that of female flies in every group.The percent survival of male flies is significant lower than that of female flies after 40 days.The unbalance between SOD and MDA could be one of the factors causing aging and death.