Abstract: Experimental study of regulated deficit irrigation at different growth stages was carried out in Tianjiazha irrigation experimental station of Zhangye City in Hexi Corridor.Under the condition of keeping soil moisture at other growth stages as normal irrigation（soil moisture threshold 65%～75%），in the seedling stage，tuber formation stage，tuber expansion stage and starch accumulation period of potato were treated with mild deficit（soil moisture threshold 55%～65%）.Normal irrigation in the whole growth period was used as control，the physiological indexes，yield and water use of potato were determined.Test results showed that plant height，stem diameter and total biomass per plant decreased at different growth stages.Among them，the degree of water deficit was most significant in the tuber expansion period.Regulated deficit treatment，the yield of potato was 33 027.22 kg/hm2 at a slight water deficit in seedling stage，but there was no significant difference between control and adequate water supply.Water use efficiency and irrigation water use efficiency were the highest，reached 6.91 and 9.38 kg/m3 ，and it could significantly improve overall quality of potato.Potato yield and water use efficiency were lowest in tuber formation stage，only 24 047.32 kg/hm2 and 5.85 kg/m3，and the quality of potato decreased.Therefore，drip irrigation under plastic film mulch could improve water use efficiency and irrigation water use efficiency.In addition，slight water deficit in seedling stage had a positive effect on the stability of potato yield，improving quality and water use efficiency.