Purpose <p>Due to its inherent salt tolerance and high economic value, sunflower has become a promising crop for the development of saline–alkali lands, which constitute an important reserve of cultivable land. However, sunflowers exhibit differential responses to saline-alkali soils across various regions, primarily due to variations in soil salt composition.</p> Methods <p>This study conducted a pot experiment to investigate the responses of sunflower seedlings to neutral salt, alkaline salt, and mixed salt stress (0, 60, 120,180,240 mmol L^− 1), focusing on differences in growth indicators, physiological and biochemical parameters, nutrient uptake, and ion flux.</p> Results <p>Two-way ANOVA showed that both salt type and concentration significantly affected sunflower growth and physiology. Under neutral salt stress, survival remained at 100% even at 240 mmol L^− 1, while it declined to 27.5% and 22.5% under mixed and alkaline salts, respectively, at the same concentration. Alkaline salt caused the greatest reductions in biomass, with fresh and dry weights decreasing by 29.6% and 50.0% at 240 mmol L^− 1, respectively. Mixed salt stress had intermediate effects between neutral and alkaline treatments. Membrane permeability and malondialdehyde (MDA) increased sharply under alkaline stress, indicating severe oxidative damage, while chlorophyll increased slightly (up to 20.2%) under all salt types at moderate levels. Na⁺ accumulation was highest under alkaline salt stress, accompanied by 90.1%-99.08% reductions in K⁺/Na⁺ and Ca²⁺/Na⁺ ratios. Correlation analysis showed that sunflower growth was positively associated with K⁺ and Ca²⁺ levels and negatively with Na⁺ and membrane permeability, highlighting the key role of ionic balance in salt tolerance.</p> Conclusions <p>Higher concentrations of neutral salt exerted more severe adverse effects on sunflowers. In contrast, alkaline salt stress showed a dual effect that the low concentrations stimulated sunflower growth, while high concentrations inhibited it. These findings provided practical guidance for tailoring sunflower cultivation strategies to specific saline-alkali soil types.</p>