<p>The regulation of salt tolerance in crops by melatonin and abscisic acid has received extensive research and exploration, but the interaction between the two hormones is still unclear, especially in terms of ion homeostasis and energy supply. This study pretreated rice seedling (via leaf spraying) with melatonin, abscisic acid, and their synthetic inhibitors, focusing on exploring the interaction between melatonin and abscisic acid in regulating rice ATP metabolism, NADPH metabolism, carbohydrate accumulation, and Na⁺/K⁺ homeostasis under salt stress. The results showed that melatonin could alleviate salt sensitivity in rice caused by abscisic acid deficiency, specifically manifested in an increase of 12.77% in root dry weight and 4.53% in salt tolerance index. In terms of regulating Na⁺/K⁺ homeostasis, melatonin and abscisic acid exhibit complementarity. Melatonin compensates for the decrease in carbohydrates caused by abscisic acid deficiency, specifically manifested as total soluble sugars, starch, NSC, glucose and fructose increased by 12.7%, 12.2%, 12.4%, 10.3%, and 9.1%, respectively, thereby increasing energy supply. The structural equation modeling results indicate that NADPH metabolism and carbohydrate content are important factors affecting Na⁺/K⁺ homeostasis, with path coefficients of 0.663 and 0.306, respectively. In summary, melatonin alleviates the Na⁺/K⁺ homeostasis caused by abscisic acid deficiency in rice under salt stress by regulating energy supply.</p>