Abstract: 【Objective】 To clarify the impact of deficit irrigation on the yield and water use efficiency of machine-picked cotton in Xinjiang under the condition of drip irrigation under mulch. 【Method】 In this study, five irrigation quotas treatments were conducted with 225 mm (Ir₁), 285 mm (Ir₂), 345 mm (Ir₃), 405 mm (Ir₄) and 465 mm in a typical cotton harvesting area in Xinjiang. The effects on the water consumption characteristics, dry matter accumulation and cotton yield formation of different deficit irrigation quotas were analyzed in cotton field from 2016 to 2018. 【Result】 The results showed that with the increase of irrigation quota, the water consumption of cotton fields showed an increasing trend, and the water consumption modulus coefficient in the later stage of cotton growth was increased, so that the dry matter accumulation speed was faster, the rapid accumulation period was longer, but the irrigation amount increased. The dry matter distribution of cotton bolls first increased and then decreased. The maximum distribution of Ir₃ was 64.7-82.2 g/plant. The proportion of stems and leaves increased significantly with the increase of irrigation quota, while the proportion of cotton bolls decreased significantly; In terms of cotton yield and water use efficiency, the number of bolls per plant and the weight of bolls increased significantly with the increase of irrigation quota, which promoted the increase of seed cotton yield. Compared with other treatments, high irrigation quota achieved higher seed cotton yield of Ir₅. Among them, lint was only 3.80% higher than that of Ir₄. However, in terms of water use efficiency, water use efficiency was significantly reduced with the increase of irrigation. Among them, Ir₁ was 20.59%, 34.59%, 48.68% and 57.93% higher than those of Ir₂-Ir₅, respectively. 【Conclusion】 In summary, under the condition of deficit irrigation, the water supply function of the soil can be fully exerted, and deficit irrigation can be carried out appropriately, which is conducive to the transfer of dry matter accumulation to the reproductive organs, resulting in the number of bolls per plant and the weight of boll significant improvement. Therefore, on the basis of the actual water consumption during the cotton growth period, reducing the irrigation amount by 12% will not significantly reduce the cotton yield, and at the same time, higher water use efficiency can be obtained.