The investigation of the response mechanisms of Cyperus esculentus to water and salt stresses is crucial for the enhancement of the productivity of saline soils. Previous studies have indicated that plant hormones, antioxidant systems, and osmoregulation may contribute to the stabilization of yield. However, the contributions and interactions of these mechanisms remain poorly understood under combined water and salt stress in natural environments. A dual-factor (salt and water) orthogonal test was used to investigate the growth and biochemical responses of C. esculentus, under combined salt and water stress in a field experiment conducted on a typical saline area in northern China. The findings reveal that C. esculentus adjusted its biomass allocation strategies and activated hormone responses, antioxidant system, and osmoregulation mechanisms to maintain stable yield. Due to the negative synergism when salt and water stress coexist, the homogeneous limitations of both are weakened. Thus, the key to maintaining yields under combined water and salt stress may depend on indirectly enhancing tolerance to oxidative damage through abscisic acid, rather than focusing on accumulating low molecular weight osmoregulants and antioxidant enzymes to directly alleviate homogeneous limitations. Also, under combined salt and water stress, insufficient irrigation may have a greater impact on morphological characteristics than high salinity. The above results contribute to a deeper understanding of the process of adapting C. esculentus to combined salt and water stress.