Object: Media trust is one of the essential factors affecting health behavior. Based on the protection motivation theory (PMT), this study explores the impact of different public media trust (traditional media, social media, interpersonal communication) on future COVID-19 vaccine motivation. Methods: The online survey was conducted from 14 April to 30 April 2021, and 2098 adults were recruited to participate in the online survey through the Wenjuanxing online survey platform. The survey included the PMT constructs (threat appraisal, coping appraisal, and motivation for future COVID-19 vaccination), trust in different media, vaccine hesitation reasons, and implementation of other non-pharmaceutical interventions. Structural equation model (SEM) was used for latent variable analysis, and Spearman linear correlation coefficient matrix was used to explore the relationships between variables. Results: In terms of trust in different media, participants who had a higher education level (p = 0.038), who was married (p = 0.002), and who had not been vaccinated against COVID-19 during the survey (p = 0.002) show greater trust in traditional media. Participants who were married (p = 0.001), who had a relatively high income (p = 0.020), and who had not been vaccinated (p = 0.044) show greater trust in social media. Older participants (p < 0.001) and married (p < 0.001) showed greater trust in interpersonal communication. In the structural equation, trust in traditional media had a direct positive impact on perceived severity (β = 0.172, p < 0.001) and a direct negative impact on internal rewards (β = −0.061, p < 0.05). Trust in both traditional and social media separately had a direct positive impact on self-efficacy (β = 0.327, p < 0.001; β = 0.138, p < 0.001) and response efficiency (β = 0.250, p < 0.001; β = 0.097, p < 0.05) and a direct negative impact on response costs (β = −0.329, p < 0.001; β = −0.114, p < 0.001). Trust in interpersonal communication had a direct positive impact on external rewards (β = 0.186, p < 0.001) and response costs (β = 0.091, p < 0.001). Overall, traditional media trust had an indirect positive influence on vaccine motivation (β = 0.311), social media trust had an indirect positive influence on vaccine motivation (β = 0.110), and interpersonal communication had an indirect negative influence on vaccine motivation (β = −0.022). Conclusion: This study supports the use of PMT as an intermediate variable to explore the effect of media trust on vaccination intention. High trust in traditional media has helped reduce vaccine hesitation, increased the public’s future COVID-19 vaccination motivation, and maintained other non-pharmacological interventions. Social media also had a certain promotion effect on vaccine motivation. In this context, attention should also be paid to interpersonal communication, and the science publicity work was suggested for an individual’s family members and friends in the future to improve the quality and ability of interpersonal communication.