Objective To investigate the current situation of medical students' medical belief and to analyze the influencing factors, so as to provide the basis for improving their medical belief. Methods From January to February 2021, the five-year and eight-year medical undergraduates of Shanghai Jiao Tong University School of Medicine enrolled from 2017 to 2020 were selected as the survey subjects. A self-made questionnaire was used to investigate their medical belief, and the influencing factors were analyzed by multiple linear regression method. Results A total of 778 medical students participated in the survey and the score of medical belief was 88.72±16.83. The results of multiple liner regression analysis showed that the frequency of participating in activities such as lectures (b=0.130, P<0.001), help obtained during learning process (b=0.204, P<0.001), humanistic education level of faculty (b=0.085, P=0.014), effect of teaching method like case-based learning (b=0.245, P<0.001), degree of help from career planning courses (b=0.067, P=0.028) and views that the doctor-patient relationship will gradually improve in the future (b=0.088, P=0.002) are related to one's medical belief. In population with following characteristics like female, higher grades (junior and above) and those with required courses scores ranking on bottom 50% of required courses scores have a weaker belief while the males (b=0.094, P<0.001), lower grades (b=0.109, P<0.001) and ranking on top 50% of required courses scores (b=0.136, P<0.001) have stronger medical belief. The above variables can explain 46.8% of the variation in medical belief. Conclusions There is still space for further improvement in medical students' belief. The teaching resources and supports obtained by medical students during learning process and their views on the doctor-patient relationship in the future are the influencing factors of medical belief. It is recommended to improve career planning and enrich humanistic education, optimize lectures and encourage volunteer activity, and enrich teaching methods to improve medical students' medical belief. More attention should be paid to students of females, higher grades and those with lower scores. Media support is also necessary to improve the doctor-patient relationship, which further strengthen students' medical belief.