The emergence of virtual influencers and AI doctors has significantly increased the attention of Chinese users, especially their health awareness and cancer health literacy. In our current study, guided by parasocial relationship theory, we examined the psychological antecedents that influence Chinese young adults’ willingness to engage in liver cancer prevention. Specifically, we aimed to examine the mediated mechanism of reduced unrealistic optimism within this relationship. A total of 252 respondents participated in this study, and the valid data were analyzed using hierarchical regression and mediation analysis to test our hypotheses. The results demonstrated three positive correlations between psychological factors (including perceived severity, parasocial relationship, and response efficacy) and Chinese young adults’ willingness to engage in liver cancer prevention. Furthermore, we found that reduced unrealistic optimism mediated these relationships. These findings provide valuable practical insights for Chinese health departments and experts to develop effective health campaign strategies that utilize multiple media platforms for optimal promotion.