Abstract: [Purpose/Significance] This paper aims to explore the relationship between online health information search behavior and health anxiety, and the role mechanism of uncertainty factors in it, so as to provide a reference for individuals to alleviate health anxiety and manage health uncertainty. [Design/Methodology] A mixed-method approach combining empirical sampling method and post hoc interviews was used to study the action of users' health information search behavior in relation to their health anxiety, and to construct a process model of the uncertainty factors' evolution along with the search stage on this basis. [Findings /Conclusions] Users' individual cognitive uncertainty and uncertainty in the external information environment jointly contribute to the relationship between their online health information search and health anxiety, resulting in not only a single-dimensional linear link between the two, but also a cyclical and non-linear relationship. As the search process unfolds, the uncertainty factors in the nonlinear relationship show an evolutionary pattern, within which both the uncertainty factors affecting the search behavior and the significance of their roles vary at different stages of the information search process. In particularly, for individuals suffering from a disease, uncertainty may signify the hope of treatment and the chance of recovery. [Originality/Value] This study introduces uncertainty factors in the study of users' health information behavior, providing new perspectives and directions for better understanding the relationship between health information search behavior and health anxiety.

Keywords: Health information seeking behavior, Health anxiety, Uncertainty, Experience sampling method, Ternary interaction model