Background: Physical sub-health is directly related to people's work effectiveness and quality of life. Sub-health prevention has become an urgent medical problem. Current research on sub-health mainly focuses on the diagnosis, influencing factors and treatment. Based on the proposed physical sub-health risk perception scale, we explore the differences in the demographic factors and the mechanism of risk perception level on physical sub-health to provide data support for the management of public physical sub-health.Methods: Clinical and risk perception data were collected from 770 physical examinees, which were analyzed using SPSS 23.0, R, and Python software. Pearson correlation coefficient was used to investigate the correlation and multiple stepwise regression analysis was used to explore the influence of demographic variables on physical sub-health and risk perception. Also, this study used a two-way interaction moderated multiple regression approach to examine the moderating effects of demographic variables on physical sub-health and risk perception.Results: Attribute of living place, sub-health duration, marital status, average annual household income, risk perception level were negatively associated with physical sub-health (r= -0.07 ~ -0.17, P < 0.05). The risk perception level was positively correlated with education, attribute of living place,average annual household income, sub-health duration, number of employees in the unit and sub-health proportion in the unit (r= 0.09 ~0.26, P<0.05), but negatively correlated with age (r= -0.11, P<0.05). The number of children had a moderating effect on physical sub-health and risk perception (Interaction coefficient α= -0.3, P<0.05).Conclusions: The factors directly affecting the physical sub-health included age, education, attribute of living place,sub-health duration and sub-health proportion in the unit, while the risk perception level, marital status and average annual household income were found to be indirect influencing factors. The number of children had a moderating effect on physical sub-health and risk perception. Therefore, we suggest attaching importance to public physical exercise and health checkups, correctly guiding public risk perception, and spreading the national policy of bearing and rearing better children etc. to promote the development of public physical health in China.