Abstract: In order to explore the effects of different irrigation timing and water temperature on the physiological characteristics and yield of cotton under mulched drip irrigation, four irrigation water temperature levels were set as 15.00（normal irrigation water temperature）, 20.00, 25.00, and 30.00 ℃, and two irrigation timing levels were daytime and nighttime（denoted as DW and NW, respectively） for a complete combined design, with a total of eight treatments. The results show that warming irrigation advances the growth process of cotton, promotes the growth of plant height, stem diameter and leaf area of cotton, and is conducive to the photosynthesis of cotton. The effect of warming irrigation at night is more significant. Warming irrigation significantly increases seed cotton yield by 2.95%-14.13%, and nighttime irrigation increases cotton yield by 3.34% compared with daytime irrigation. Based on regression analysis, it is determined that the best irrigation time to increase cotton yield is at night, the best irrigation water temperature was 26.38 ℃, and the corresponding yield is 7 482.96 kg/hm~2. The results can provide theoretical basis and technical reference for the implementation of warming irrigation technology for drip irrigation cotton under film in northern Xinjiang.