Abstract: Using fruit fly (Drosophila melanogaster) survival experiment, we investigated the antioxidant and antiaging functions of grapefruit juice in vitro.Low dose (5%) 、middle dose (10%) and high dose (20%) of grapefruit juice were added into the basic medium for fruit fly respectively, the average lifespan and the highest lifespan of the fruit flies fed in three groups were calculated.Moreover, SOD activity and MDA content in the homogenate of fruit fly body were determined.The results showed that, with low, middle and high dosages, the grapefruit juice significantly prolonged the average lifespan of male fruit flies by 8.24%, 20.06%and 13.50%, respectively, while 12.04%, 24.93% and 19.33% for it of the female fruit flies, respectively.Feeding grapefruit juice in certain concentrate could improve SOD activity and reduce MDA content for both male and female fruit flies.The data from middle dose group showed the best effects which coincide with the results of fruit fly survival experiment.