Purpose This study aims to investigate the relationship between undergraduates' health literacy, health behavior self-efficacy, and health-promoting lifestyles. Method In April 2021, a survey was conducted with 1050 undergraduates from 9 universities in Jiangxi Province, utilizing Health Literacy Scales, Health Behavior Self-efficacy Scales, and Health-Promoting Lifestyle Revision Scales. Results (1) The average health literacy score among undergraduates was (66.17±10.01), with 81.6% of students having high or marginal health literacy. The average score for health-promoting lifestyles was (101.34±16.09), indicating an above-average level. The total score for health behavior self-efficacy was (89.23±18.43), indicating a general level of self-efficacy. (2) Positive correlations were found between undergraduates' health literacy, health behavior self-efficacy, and health-promoting lifestyles (r=0.259 ~ 0.759, P < 0.05). (3) Health behavior self-efficacy was found to mediate the relationship between undergraduates' health literacy and health-promoting lifestyles. Conclusion  To promote a healthy lifestyle among undergraduates, it is crucial to not only improve their health literacy but also enhance their health behavior self-efficacy.