Based on the objective data collected from Online Health Community (OHC), the paper analyzes the dual influences of user attributes and network structure on users' online health knowledge sharing behavior. The results show that both online reputation and degree centrality positively influence users' health knowledge sharing behavior. Degree centrality negatively moderates the relationship between online reputation and users' health knowledge sharing behavior, while closeness centrality positively moderates the relationship between online reputation and users' health knowledge sharing behavior.