Water scarcity constrains cotton production in arid regions, while film mulching and magnetized irrigation have demonstrated agronomic potential individually, their combined effects on rhizosphere dynamics and soil aeration remain unclear. A two-year field study (2023-2024) employed a two-factor completely randomized design with three replicate units (106 x 200 m) per treatment. The impacts of magnetized irrigation (0.3 T) and three film mulched widths (1.4, 2.05, and 4.4 m) were evaluated. Outcomes assessed included soil oxygen (O2) and moisture dynamics, rhizosphere microbial, and irrigation water use efficiency (IWUE). Ultra-width mulched with magnetized irrigation (W3A) synergistically optimized soil O2 (15.7-20.0 %) and enhanced moisture retention by 20.4 % compared to narrower mulches. This combination boosted microbial diversity and metabolic activity, increasing actinobacteria abundance (17.1-25.5 %) and elevating predicted carbohydrate metabolism pathway abundance based on 16S rRNA profiling (1961 f 175 reads) by 1.5-fold versus non-magnetized treatments. W3A maximized root dry weight (35.9 g plant-1) and seed cotton yield (7950 f 364 kg hm-2 in 2024), significantly outperforming non-magnetized (6600 f 460 kg hm-2) while achieving IWUE of 1.74 f 0.3 kg m-3. This study provides novel evidence that integrating magnetized irrigation with wide mulching enhances yield by creating a favorable soil water-oxygen environment, optimizing rhizosphere processes, and predicting microbial function, thereby offering a sustainable technological framework for arid agriculture.