[Purpose/significance] The outbreak of infodemic in public health emergencies is a big challenge for public health communication and patient education. Information overload, a state that users are overwhelmed by too much information or mis- /dis-information, is a primary manifestation of infodemic in the era of global information flow. [Method/process] This paper used the novel coronavirus disease (COVID-19) as a case to illustrate how information overload can affect users' information avoidance behavior from cognitive and psychological perspectives in public health emergencies. Based on information behavior theory and stress coping theory, this paper proposed a theoretical model and several related hypotheses. The study adopted the survey approach and structural equation modeling method for data collection and analysis. [Result/conclusion] The findings showed that information overload is associated with users’negative emotions and perceived susceptibility of the COVID-19, which further resulted in a defensive motivation and reduction of exposure to health information. The study may enrich the literature of both information overload and health information behavior, and yield practical implications for coping with infodemic in public health emergencies.