Abstract: 【Purpose/significance】Social support is an important driving factor of users’knowledge sharing in virtual health commu-
nity.It is necessary to systematically explain the internal mechanism and boundary conditions of user s’health knowledge sharing
stimulated by social support.【Method/process】Based on social support and cognitive-affective system theory, it constructed a chain
mediation model of the impact of social support on health knowledge sharing through trust and community belonging, and discussed
the moderating effect of perceived self-efficacy.286 valid data were collected by questionnaire survey for empirical analysis【. Result/
conclusion】The findings show that: social support has a significant positive impact on health knowledge sharing; Trust and sense of
community belonging have a chain mediating effect between social support on health knowledge sharing. Users’perceived self?efficacy can reinforce the chain mediation path. The higher perceived self-efficacy is, the stronger the positive role of social support
on health knowledge sharing, as well as the chain mediation roles of trust and sense of community belonging between social support
and health knowledge sharing.【Innovation/limitation】This paper uses cognitive-affective system theory to explain the influence
mechanism of social support on health knowledge sharing, which enriches the research achievements in the field of users’health in-
formation behavior.