COVID-19 epidemic, which erupted and spread around the world at the end of 2019, is still threatening people's lives and health. The COVID-19 vaccine is considered to be the most effective way to prevent individuals from infecting COVID-19 epidemic. However, people still hesitate to think about vaccine efficacy and vaccine safety in the risk situation. Hence, the study aims to explore and assess the influencing factors of Chinese public’s willingness to vaccinate, and put forward targeted suggestions for the booster shot promotion. We expand on the basis of Health Belief Model(HBM) and Planned Behavior Theory(PBT), and conduct a questionnaire survey on 1032 respondents using health belief scale, social media attention scale, government trust scale and prosocialness scale. The results show that  (1) vaccine perceived benefits, vaccine perceived risks, epidemic perceived risks, social media attention, prosocialness and government trust have a significant impact on COVID-19 vaccine willingness; (2) vaccine perceived benefits and vaccine perceived risks play a mediate role between government trust and vaccine willingness; (3) perceived risk of epidemic situation plays a mediate role between social media attention and vaccine willingness; (4) prosocialness plays a mediate role between the perceived risk of the epidemic and the willingness to vaccinate.