A field experiment was conducted to test the effect of mulched drip irrigation under water deficit regulation (WDR) on leaf photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), tuber yield and potato water use in oasis irrigation region. The results showed that Pn , Tr and Gs were reduced by WDR during different potato growth stages. No obvious difference was found in Pn before and after re-watering of potato, but Tr and Gs were obviously improved. Potato yield was not decreased by low WDR during tuber initiation, but was significantly (p＜0.05) decreased in the medium WDR plots during tuber initiation and low and medium WDR plots during tuber bulking. Periodic water consumption of potato was greatly affected by WDR, and the higher soil water deficit, the less potato periodic water consumption. In addition, the total water consumption throughout the whole growing season was significantly lower in all the WDR potatoes than that in full irrigation plots (CK). The highest water use efficiency (WUE) was maintained in low WDR potato during tuber initiation, significantly improved by 36.2%, 32.4% and 14.2% than that in medium WDR plots during tuber bulking, low WDR plots during potato starch accumulation and CK, respectively. Therefore, mulched drip irrigation under WDR may reduce Pn, Tr, Gs, and periodic and total water consumption of potato, but its WUE can be greatly improved. In addition, potato yield will not be reduced by mulched drip irrigation under low WDR during tuber initiation.