Abstract: Alfalfa (Medicago sativa L.) is primarily cultivated in regions of Northeast, North, and Northwest China where soil salinization is severe, making it susceptible to salt stress and resulting in yield losses. This study investigated the alleviating effects of exogenous gibberellin (GA) seed soaking on alfalfa under salt stress and the relationship between optimal GA soaking concentration and salt stress levels. The experiment employed three salt stress levels (0.3%, 0.6%, and 0.9%) and three GA soaking concentrations (50, 100, and 150 mg/L). Biomass, antioxidant enzyme activity, ion content, and hormone levels in alfalfa seedlings were measured. Results showed that appropriate GA concentrations alleviated salt stress by increasing antioxidant enzyme activity, potassium ions, auxins, and salicylic acid content, while reducing abscisic acid, chloride ions, and sodium ions in alfalfa seedlings under salt stress. The optimal GA concentration was inversely proportional to salt stress intensity: 100-150 mg/L GA was most effective under 0.3% salt stress, approximately 100 mg/L under 0.6% salt stress, and around 50 mg/L under 0.9% salt stress. High concentrations of both salt and GA exhibited synergistic inhibitory effects on alfalfa seedlings. This study demonstrates that exogenous GA seed soaking can mitigate salt stress toxicity in alfalfa seedlings, promote their growth, and is more effective under low to moderate salt stress compared to severe salt stress. These findings provide theoretical basis and practical guidance for improving alfalfa cultivation in salt-affected regions.