Abstract: 【Objective】 To study the effects of irrigation amount and planting density on photosynthetic characteristics and yield of drip irrigation membrane-free cotton. 【Method】 Field tests designed by the two-factor split zone were carried out with "medium 619" as the test material, the main area was irrigation amount, which was 3,000 m³/hm² (W₁), 4,500 m³/hm² (W₂) and 6,000 m³/hm² (W₃), respectively; the sub-area was density, which was 29.24×10⁴/hm²(M₁), 26.32×10⁴/hm² (M₂), 23.92×10⁴/hm² (M₃) and 21.93×10⁴/hm² (M₄), respectively, to study the dynamics of membrane-free cotton population leaf area index (LAI), photolysis indicators and yield differences. 【Results】 Full-blooming stage was the maximum period of filmless cotton LAI and photolysis function, and the LAI increased with density and irrigation amount.The LAI change of W₂M₃treatment was more stable and higher in the later stage.The LAI of W₃M₁ treatment was the highest, but it decreased rapidly after the full flowering stage.Suitable irrigation and reasonable density were beneficial to the improvement of photosynthetic function of leaves.The treatments W₂M₃, W₂M₄ and W₃M₃ had higher P_n, G_s and T_r and lower C_i at full flowering stage, and the diurnal photosynthetic "midday depression" was not obvious, and its maximum values were 29.10-32.15 μmolCO₂/(m ²·s), 0.91-1.07 mol/(m²·s), 12.78-13.87 mmolH₂O /(m²·s) and 112.1-131.0 μmolCO₂/mol, respectively, and the yield reached a high level of 6,890.71-7,496.79 kg/hm².Although the LAI and photosynthetic index of W₃M₄ treatment were higher, they decreased too fast in the later stage, while the W₁M₁ showed the lowest, indicating that too high or too low irrigation and density were not conducive to the improvement of photosynthetic function of leaves.The effects of irrigation amount and density on leaf growth and photosynthetic index had interaction effect, and the effect of density was higher than that of water. 【Conclusion】 Through analysis, the suitable irrigation amount and planting density in this region are 4,500-6,000 m³/hm² and 21.93×10⁴-23.62×10⁴/hm².The highest yield is 7,508.82 kg/hm² when the irrigation amount is 5,034.73 m³/hm² and the planting density is 24.63 × 10 ⁴ /hm².