Purpose The COVID-19 pandemic sets specific circumstances that may accelerate academic procrastination behavior of medical students. Career calling is a protective factor that fights against academic procrastination and may further improve medical students’ mental health and academic achievement. This study aims to determine the status of Chinese medical students’ academic procrastination during controlled COVID-19 pandemic. Moreover, the study investigates the relationships and mechanisms among career calling, peer pressure, a positive learning environment, and academic procrastination. Patients and Methods Data were collected from several Chinese medical universities through an anonymous cross-sectional survey of 3614 respondents (effective response rate = 60.0%). Using online questionnaires to collect the data and IBM SPSS Statistics 22.0 for statistical analysis. Results The average score of academic procrastination of Chinese medical students was 2.62±0.86. This study proved the usage of peer pressure and positive learning environment as moderating roles of relationship between career calling and academic procrastination. Career calling was negatively correlated with academic procrastination ( r = −0.232, p < 0.01), while it was positively correlated with peer pressure ( r = 0.390, p < 0.01) and a positive learning environment ( r = 0.339, p < 0.01). Moreover, academic procrastination was negatively correlated with peer pressure ( r = −0.279, p < 0.01) and a positive learning environment ( r = −0.242, p < 0.01). Peer pressure was positively correlated with a positive learning environment ( r = 0.637, p < 0.01). Conclusion The findings emphasize the importance of constructive peer pressure and a positive learning environment that discourages academic procrastination. Educators should highlight medical career calling education by offering related courses to fight against academic procrastination.