Abstract： Objective:To investigate the level of 25-hydroxyvitamin D［25（OH）D］in naval personnel and analyze its influencing factors，so as to provide a point of reference for the prevention and treatment of 25（OH）D deficiency in naval personnel.Methods:By using the method of cluster sampling，the crew of a naval troop were divided into six groups according to the ships，from which a group of 62 crew members were randomly selected as the subject of the investigation into experimental group，and 60 land-based naval personnel were randomly selected as the control group. The levels of serum 25（OH）D in both groups were tested.Results:The level of serum 25（OH）D in the experimental group was（18.8 ± 5.5）ng/ml，and that in the control group was（28.7 ± 6.4）ng/ml with a statistically significant difference between them（ P<0.05）. There were statistically significant differences in the level of serum 25（OH）D among different age groups of the experimental group，in which those aged 35 and above having the lowest level of 25（OH）D. There was no statistically significant difference in the level of serum 25（OH）D among different age groups within the control group（ P>0.05）. It was found the level of 25（OH）D was significantly lower in the crew members who have been serving for six to nine years and over 10 years than those who have served less than five years with statistically significant differences（ P<0.05）. Conclusion:The 25（OH）D level of onboard naval personnel was significantly lower than that of the land-based personnel with less than 20% of the tested subjects reaching the normal level，and the 25（OH）D level of naval personnel was closely related to age and onboard service time.