Introduction Freshwater scarcity and soil salinization constrain agricultural production in arid and semi-arid regions. Freezing saline water irrigation (FSWI) offers a potential strategy for using saline water during the freeze-thaw period, but the optimal irrigation amount and its yield-driving mechanisms remain unclear.Methods Here, a three-year field experiment was conducted from 2022 to 2024 in Dalad Banner, Inner Mongolia, China, with four FSWI treatments of 0, 90, 180 and 270 mm. We evaluated pre-sowing soil hydrothermal, salinity and microbial functional indicators, and assessed sunflower growth, yield and seed quality under uniform agronomic management.Results Among the treatments, FSWI180 showed the best overall performance. It maintained favorable pre-sowing soil moisture and salinity conditions, increased yield by 93% relative to the non-irrigated control, and improved seed oil content to 43.96%. It also achieved the highest comprehensive growth and quality indices, with mean GI and QI values of 2.126 and 1.182, respectively. XGBoost-SHAP analysis identified soil moisture, total salinity, electrical conductivity and community robustness as the main yield-driving factors, together accounting for 74.75% of the total contribution.Discussion These results indicate that 180 mm FSWI can coordinate soil water storage, salinity regulation and microbial functional stability, thereby supporting stable yield improvement and high-quality sunflower production in cold arid saline-alkali regions.