Abstract: In order to find out the suitable aerated irrigation mode for drip irrigation cotton in arid area of Northwest China, five aerated irrigation treatments were set up with non-aerated irrigation as control（CK）: aerated irrigation at seedling stage（AS）, aerated irrigation at budding stage（AB）, aerated irrigation at flowering and boll stage（AF）, aerated irrigation at budding stage + aerated irrigation at flowering and boll stage（ABF）, and aerated irrigation at seedling stage + aerated irrigation at budding stage + aerated irrigation at flowering and boll stage（AW）. The effect of aerated irrigation at different growth stages on the photosynthesis and water use efficiency of cotton in arid areas of Northwest China was studied. The results show that compared with CK, the photosynthetic characteristics and aboveground biomass of all aerated treatments are significantly increased. Among them, the net photosynthetic rate of aerated treatment is significantly increased by 22.68%, the transpiration rate is significantly increased by 41.19%, the stomatal conductance is significantly increased by 33.42%, and the intercellular CO₂ concentration is significantly decreased by 16.22%, respectively. Aerated irrigation at the flowering and boll stage significantly increases the dry matter accumulation of stems, leaves and buds/bolls by 29.26%, 11.15% and 33.41%, respectively. Under aerated irrigation at different growth stages, the optimal treatments for cotton photosynthetic characteristics, aboveground biomass and yield are AW and AF, and there is no significant difference. However, the water use efficiency of AF treatment is the highest, which is 1.51 kg/m~3, significantly higher than that of AW treatment. Therefore, from the perspective of efficient water-saving and yield-increasing, aerated irrigation at the flowering and boll stage（AF） of cotton can be used as the best aeration irrigation mode for cotton under mulched drip irrigation in arid areas of Northwest China.