Soil salinity severely limits cotton production in arid regions of Xinjiang, China, where efficient irrigation water management is essential. This study aimed to identify an optimal combination of leaching amounts and drip irrigation types to regulate root-zone water and salinity, while ensuring stable yield and fiber quality under water-saving conditions. A three-year field experiment (2020-2022) was conducted on saline-alkali land in Xinjiang, China, comparing surface and subsurface drip irrigation (DI and SDI) under three leaching amounts (120, 240, and 360 mm), with non-leached surface drip irrigation as the control. The results showed that leaching amount was the primary factor governing the water-salt environment in the cotton root zone and subsequent crop performance. Moderate leaching (240 mm) effectively alleviated salinity stress, promoted biomass accumulation and reproductive allocation during critical growth stages and significantly improved cotton yield stability and fiber quality. At low leaching amount (120 mm), SDI showed advantages in salt control and yield improvement compared with DI, whereas differences between irrigation systems diminished under moderate leaching. Excessive leaching did not further improve yield or quality and reduced irrigation water productivity. Overall, applying a moderate leaching amount (240 mm) in combination with either DI or SDI achieves a favorable balance between salt regulation, water-use efficiency and stable cotton production. These findings provide practical guidance for irrigation water management in saline-alkali soils of arid regions.