Soil salinization and freshwater scarcity are major challenges for sustainable agriculture in arid and semi-arid regions. To explore strategies for improving upland cotton (Gossypium hirsutum L.) productivity, a three-year field experiment (2022-2024) evaluated the effects of magnetoelectric activated brackish water and bioelectrical regulators. Treatments included different types of irrigation water and regulator dilutions, with measurements covering leaf nutrients, photosynthesis, antioxidant activity, redox status, hormones, yield, and fiber quality. Results showed that combining magnetoelectric activated brackish water with a 400-fold diluted regulator markedly enhanced cotton performance. Leaf area index (LAI) increased up to 132.71 %, SPAD and net photosynthetic rate (Pn) improved by 28.84 % - 60.17 %, respectively, and leaf N, P, and K reached maximums of 32.97 g/kg, 6.67 g/kg, and 33.84 g/kg. Antioxidant capacity was enhanced with maximum TAC 30.50 mu mol Trolox/g, SOD 1624.07 U/g, and CAT 82.17 mu mol/min/g, while MDA decreased to 24.54 nmol/g. Endogenous hormones showed IAA up to 26.24 mu g/kg and ABA reduced to 0.65 mu g/kg. Yield reached 9512 kg/ha, with effective boll number 6.94 per plant, ginning outturn 0.63, single boll weight 5.48 g, and fiber quality index (FQI) improved by 56.50 %. Leaf Quality Index (LQI) was strongly correlated with yield and FQI, highlighting the physiological basis of high productivity and fiber quality. In conclusion, the integration of magnetoelectric activated brackish water with a 400-fold diluted bioelectrical regulator effectively enhanced leaf physiology, yield, and fiber quality, providing a scientific basis for high-yield, high-quality cotton cultivation in arid and semi-arid regions and guidance for future large-scale applications.