Understanding drought response mechanisms is critical for high-efficiency maize production in the seasonally arid regions of Southwest China. A two-year field experiment (2022-2023) was conducted using a randomized block design with two deficit degrees (D25% and D50%) imposed at single or multi stages to investigate summer maize growth, yield and water use responses to stage-specific deficit irrigation (DI). The study site is located in a typical seasonally arid region with subtropical climate. Results indicated that DI during vegetative growth (VG) period significantly inhibited maize morpho-physiological traits (p < 0.05) but triggered compensatory recovery after reirrigation, and enhanced instantaneous water use efficiency and grain dry matter proportion (7.75%-12.52% higher than CK). Conversely, DI during reproductive growth (RG) period markedly decreased grain yield and protein content. DI at VG and early RG period also effectively increased starch content by 2.38%-15.78%. Moreover, deficit degree and stage generally significantly affected maize morpho-physiological traits, dry matter, yield and quality (p < 0.05). Entropy-TOPSIS evaluation identified the D25% treatment at seedling stage as the optimal strategy, as it maintained yield stability (4.52% reduction, p > 0.05) while enhancing water use efficiency (3.26%). We conclude that stage-specific DI serves as a practical, climate-adaptive tool for summer maize production in seasonally arid regions.