Abundant health knowledge resources are available on social media to facilitate technology-enhanced knowledge learning among older adults. The objective of this study is to investigate the predictors and the underlying formation mechanism of older adults' intention to learn health knowledge on social media. We propose a novel model to examine how older adults' emotional state (i.e., health anxiety) and cognitive state (i.e., e-health literacy) during knowledge acquisition influence threat appraisal (i.e. perceived severity and perceived susceptibility) and coping appraisal (i.e. self-efficacy and perceived benefits), thereby shaping older adults' intention to learn health knowledge. Survey data from 337 Chinese older adult users of social media was collected to test the research model. Results reveal that perceived susceptibility, self-efficacy and perceived benefits exert positive effects on older adults' health knowledge learning intention, while the impact of perceived severity on health knowledge learning intention is not statistically significant; health anxiety is positively correlated with perceived severity and perceived susceptibility, and e-health literacy is a powerful predictor of self-efficacy and perceived benefits. This paper enriches the literature related to technology-enhanced knowledge learning and online health behavior among older adults. Effective strategies are proposed based on the findings for practitioners dedicated to promoting health knowledge via social media and older adults who apply health knowledge to address health-related needs.