Abstract: Canopy photosynthetically active radiation interception rate (PARI) is one of the important indicators for evaluating crop canopy structure. This study aims to explore the effects of different irrigation regimes on the PARI of cotton canopy under non-film drip irrigation as well as the mechanism of canopy PARI regulating the growth and yield formation of cotton. In 2021, an irrigation experiment without plastic film mulching was carried out in the cotton fields in Alar City, Xinjiang Uygur Autonomous Region, China. A total of four treatments were designed, namely 5 (W5), 6 (W6), 7 (W7), and 8 times (W8) irrigation for the flowering and boll-opening stage, with irrigation frequencies of 9, 8, 7, and 6 days, respectively. All treatments followed the same irrigation regime as conventional fields prior to the initial flowering stage. After the initial flowering stage, the quota of each irrigation was 69 mm for all treatments. The last irrigation quota for the W8 treatment was 52.2 mm. The total irrigation quotas for the W5, W6, W7, and W8 treatment were 366, 504, 573, and 625.2 mm, respectively. A wide-narrow row spacing planting pattern was adopted, with a wide row spacing of 66 cm and a narrow row spacing of 10 cm. The spatial gridding and Kriging interpolation methods were employed to analyze the canopy PARI at various growth stages of cotton. The cotton leaf area, plant height, stem diameter, seed cotton and lint cotton yields were also measured. The results showed that in the horizontal direction, the PARI value of the cotton canopy was higher in the narrow rows and lower in the middle of the wide rows. In the vertical direction, the PARI value decreased as the canopy height increased. Different irrigation treatments changed the maximum height of PAR interception within the cotton canopy. The maximum height of PAR interception of the W5 treatment was only 60 cm, while that of the W7 and W8 treatments was greater than 70 cm. The differences in canopy PARI between the treatments during the full-flowering stage mainly originated from the area at vertical positions 40 to 80 cm. The average PARI of the W7 treatment was the highest in the area at vertical positions 60 to 80 cm. The average PARI of the canopy at the horizontal position of 20～60 cm and the vertical position of 0～80 cm during the boll-opening stage was directly proportional to the irrigation quota. As cotton grew, the PARI in different canopy layers generally exhibited a unimodal variation pattern. Due to late maturity, the cotton plants of the narrow rows of the W8 treatment exhibited no significant decline in canopy PARI during the boll-opening stage. As the irrigation quota increased, the biomass of vegetative organs gradually increased, but the reproductive organ biomass and seed cotton yield showed a trend of increasing initially and then decreasing. The W8 treatment exhibited the highest accumulation of vegetative organ biomass, but its reproductive-organ biomass accumulation and allocation ratio were lower than those of the W7 treatment. The yields of seed cotton and lint cotton of the W7 treatment were significantly higher than those of the other treatments. Canopy PARI and cumulative canopy PAR interception were positively correlated with cotton growth parameters and biomass accumulation. The total biomass of cotton (especially reproductive organ biomass) and the accumulated PAR interception conformed to the logistic model. Multiple linear regression equation can be used to predict the relationship between cotton growth, canopy accumulated PAR interception and biomass accumulation. As the average canopy PARI increased, seed cotton yield exhibited a trend of initially increasing and then decreasing. The comprehensive analysis indicated that the irrigation regime with an irrigation frequency of 7 days, a quota of 69 mm, and 7 times irrigation for the flowering and boll-opening stage could effectively improve the canopy structure of cotton. This irrigation regime could stimulate cotton plants to effectively utilize PAR while balancing the contradiction between vegetative growth and reproductive growth, thereby ensuring the yield of cotton under non-film drip irrigation. The research findings provide theoretical basis and technical reference for establishing efficient irrigation regimes and optimizing the canopy structure of non-mulched cotton in arid regions.