A transgenic cultivar of sweet potato (TS) bearing Cu/Zn-SOD and APX genes and non-transgenic control cultivar (NT) were grown in pots under three different water treatments,including control treatment (80% of soil moisture),moderate drought stress (60% of soil moisture) and serious drought stress (40% of soil moisture).At 20 and 70 day of the stress treatments,the antioxidant enzymes,the content of soluble sugar,the photosynthetic system of TS and NT were assayed respectively,in addition with the final yield formation and the long-term water use efficiency.We studied the differences between TS and NT,in order to find out whether the over-expression of exogenous genes could enhance the yield formation and water use efficiency of sweet potato.The results showed that:(1)The activities of SOD and APX,as well as the soluble sugar content were higher in TS than that in NT,while POD showed an opposite manner.The activity of APX,contents of soluble sugars and photosynthetic rates and transpiration rate are all declined in both sweet potato types with increasing drought stress.(2)Although the photosynthetic parameters decreased from 20 d to 70 d of stress in two plant types,photosynthetic rates have no significant difference between TS and NT.(3)The yield formation of the two plant types showed the highest under moderate stress and the lowest under serious stress,respectively.Transgenic sweet potato has a higher yield formation and a smaller decrease tendency of yield formation under serious stress compared with non-transgenic sweet potato.(4)The stomatal conductances and transpiration rates of TS under the three drought treatments were significantly lower than that of NT,which resulting in a higher WUE in TS.In conclusion,the genes of Cu/Zn-SOD and APX could enhance the activities of SOD and APX,the content of soluble sugar and the water use efficiency of transgenic potato during the formation of potato tuber under drought stress.Thereafter,the yield formation could be better protected from drought stress.