Objective To analyze the present situation of health promotion lifestyle and its influencing factors of candidates for 300-m saturation diving on the sea, so as to lay a foundation for daily and sustainable health promotion for saturation diving candidates. Methods The health-promoting lifestyle scale and perceived social support scale were adopted for 37 candidate divers participating in the PLA Navy 300-m saturation diving; the relationship between the present situation of health promotion lifestyle and its influencing factors was analyzed. Results The average health promotion lifestyle score of 37 divers was 142.87±22.05, with 10 (27.03%) being general, 22 (59.46%) being good, and 5 (13.51%) being excellent. The results showed that the self-actualization score was the highest (3.03±0.42), and the health duty score was the lowest (2.67±0.46). The age of the divers was negatively correlated with athletics (r=-0.516, P<0.05) and pressure managment (r=-0.517, P<0.05); the length of military service was negatively correlated with athletics (r=-0.554, P<0.05) and pressure management (r=-0.570, P<0.05). Social support was positively correlated with interpersonal relationship (r=0.831, P<0.01), health duties (r=0.802, P<0.01), nutrition (r=0.831, P<0.01), and the total score of the health promotion lifestyle (r=0.785, P<0.01). Conclusion The health promotion lifestyle of candidates for 300-m saturation diving on the sea needs to be improved and stressed. Correct lifestyle should be urged and established for divers to ensure the final completion of the mission.