Abstract: 【Objective】 To explore the influence of irrigation amount on the photosynthetic characteristics, yield and water use efficiency of southern Xinjiang short-stock dense apple. 【Method】 5-year-old Royal Gala was taken as the test tree species, conventional irrigation orchard as the control treatment (CK), and the irrigation quota was 5.14 mm, a total of 5 irrigation quotas were set, namely W₁ (13.5 mm), W₂ (18 mm), W₃ (22.5 mm), W₄ (27 mm) and W₅ (31.5 mm) to analyze the response mechanism of apple photosynthetic characteristics, yield and water use efficiency to water. 【Result】 The daily changes of net photosynthetic rate, stomatal conductance and transpiration rate of apples under different irrigation amounts all showed a single-peak curve, and reached the peak at 10:00, while the intercellular CO₂ concentration changed in the opposite way, showing an inverted "V" type, at the minimum at 10:00.At the same time, the daily average value of photosynthetic index showed a trend of first increasing and then decreasing with the increase of irrigation amount.The net photosynthetic rate, stomatal conductance, and transpiration rate were all the highest in W₄ treatment, followed by W₃ treatment.Compared with CK, W₃ treatment, and W₄ treatment, the leaf instantaneous water use efficiency increased by 5.06% and 3.37% respectively; the apple yield increased first and then decreased with the increase of irrigation amount, W₄ treatment had the highest yield, but it was not significantly different from W₃ treatment, increased by 17.01% and 14.94%, respectively compared with CK, and the irrigation water use efficiency increased by 7.23% and 26.33% respectively compared with CK. 【Conclusion】 Therefore, considering the photosynthetic characteristics, yield and water use efficiency of apples, the irrigation quota is 472.5 mm and the irrigation frequency is 21 times, the yield of apples is higher, which can save 9.06% of irrigation water compared with conventional irrigation orchards, so it can be used as an irrigation guidance scheme for 5a Royal Gala apples in southern Xinjiang.