Abstract: In order to improve the water production efficiency of crops and alleviate the agricultural water crisis,the regulated deficit irrigation mode is adopted to rehydrate the tomatoes after a certain period of drought during the flowering and fruit-bearing period. By measuring the photosynthetic parameters and chlorophyll fluorescence before and after depletion-rewatering,the physiological performance,yield and water use efficiency of tomatoes under drought-rewatering mode are analyzed. a control,3 drought periods,3 irrigation gradients,a total of10 treatments are set up. The control group has always maintained the soil moisture content of the field water holding capacity of 90%～100%,and the 3 drought periods are continuous droughts for 7,14 and 21 d,and then re-watering. 3 kinds of irrigation gradient treatments keep the soil moisture content at 80%,60% and 40% of the field hold respectively.The results show that under short-term drought stress of 7 d and 14 d,the Fv/Fm and Fv/F0 of tomato leaves decrease with the increase in stress,and recover after rewatering,except that the soil moisture is 80% of the field water holding capacity.-60% treatment can roughly restore to the control level,the rest of the treatments can not restore the state before the drought,However,each treatment after 21 days of continuous drought is more inhibited,and it can not fully recover after rewatering. During the short-term drought stress of 7 and 14 d,Ci gradually decreased,Gs decreased,and Ci recovered rapidly after rewatering,indicating that the decrease in Pn is mainly caused by stomatal restriction. In the 21 d drought treatment stage,the Ci of each regulated deficit treatment is different from Pn and the decrease in Gs,on the contrary,increases Ci compared with the 14 d drought treatment,indicating that the continuous drought for 21 days will produce non-stomata limiting factors that will reduce the Pn of tomatoes. The WUE of the soil moisture content of 80% and 60% of the field water holding capacity after 7 days of drought is higher than that of the control group by4.44% and 1.90%. It shows that controlling the soil moisture content at 80% to 60% of the field under drought conditions 7 d is conducive to improving the water use efficiency of tomatoes.Therefore,drought treatment reduces the photosynthetic performance of tomatoes,and rewatering after drought has a positive effect on improving the water use efficiency of tomatoes.