Context: The seed cotton (Gossypium hirsutum L.) yield is highly dependent on irrigation in arid and semi-arid regions around the world. However, the effects of irrigation amount on soil moisture and leaf photochemical characteristics during the drought-rewatering process, as well as canopy radiation interception and seed cotton yield of drip-irrigated cotton under film mulch remain poorly understood. Objective: The study aimed to investigate how irrigation amounts affect soil moisture distribution, leaf photochemical recovery, and canopy radiation interception following drought-rewatering in drip-irrigated cotton under film mulch. We further sought to reveal the multiscale pathways (soil-leaf-canopy) through which irrigation regulates water use and yield formation. Method: A two-season (2023-2024) field experiment was performed in the northern Xinjiang of China, with four irrigation amounts (60 %ETc, 80 %ETc, 100 %ETc and 120 %ETc, where ETc is crop evapotranspiration). Soil moisture and leaf physiology were measured on the 1st day before irrigation, 1st, 3rd, 5th and 7th days after irrigation. The photosynthetic pigments, canopy radiation and dry matter accumulation after irrigation as well as the final seed cotton yield were measured. Results: During the drought-rewatering process, high irrigation amount (120 %ETc) significantly prolonged the retention time of deep soil moisture (80-100 cm). The narrow rows and wide rows were always the main distribution areas of soil moisture, and bare soil moisture was significantly affected by soil evaporation. The leaf stomatal conductance, actual photochemical quantum effect (phi(PSII)) and electron transfer rate (ETR) showed a threshold response with increasing irrigation amount. The phi(PSII) and ETR increased by 20.4 % and 20.6 % under 120 %ETc compared with 60 %ETc, respectively. The leaf temperature and saturated water vapor pressure deficit were significantly reduced. High irrigation increased the upper layer intercepted photosynthetically active radiation (IPAR) in narrow rows by 25.9 % in 2023 and 53.5 % in 2024, but decreased it in the lower layer by 78.7 % in 2023 and 90.0 % in 2024. Total IPAR was strongly correlated with seed cotton yield (path coefficient 0.87). The 100 %ETc treatment maintained 90.4 % of the yield potential achieved while saving water under 120 %ETc demonstrating higher water-saving efficiency. Conclusion: The drought-rewatering process drives cotton yield formation through a soil-leaf-canopy cascade: soil moisture dynamics regulate leaf physiological recovery, which in turn shapes canopy light capture and assimilate partitioning. Moderately increasing irrigation (80 %-100 %ETc) can increase seed cotton yield by improving deep soil moisture, enhancing photosynthetic efficiency and optimizing canopy structure, while excessive irrigation (120 %ETc) reduces marginal benefits due to the increased light competition. Implications: The results reveal the drought-rewatering response and yield formation driving mechanism of drip-irrigated cotton under film mulch, and provide a theoretical basis for the development of precision irrigation strategies in arid areas.