The outbreak of Covid-19 had negative impacts on the mental stress and induced psychological distress among university students worldwide. This study proposed a moderated mediation model, and hypothesized that the Covid-19 pandemic-related stress was positively related to depressive symptoms among international medical students. An online survey on stress and depressive symptoms of international students was conducted in a medical university. Questions on Covid-19 pandemic-related stress, Patient Health Quesionnaire-9, Simplified Coping Style Questionnaire and the Perceived Social Support Scale were used as measurements, and model analyses were conducted using Hayes' PROCESS macro for SPSS. It was found that 9.83%, 3.08% and 2.12% students had mild, moderate and severe depressive symptoms, respectively, and the positive association between Covid-19 pandemic-related stress and depressive symptoms was significant (β = 0.27, t = 6.87, P < 0.01). Negative coping was also significantly correlated to depressive symptoms (β = 0.26, t = 6.60, P < 0.01), and partially mediated the association between Covid-19 pandemic-related stress and depressive symptoms. Perceived social support had a negative association with depressive symptoms (β=-0.26, t=-6.25, P < 0.01), played a negative moderating role in the relationship between negative coping and depressive symptoms, and moderated the indirect effect of Covid-19 pandemic-related stress on depressive symptoms via negative coping. Results of the study suggested that under the background of continuing pandemic, intervention or prevention of mental health problem is urgently needed for the international students, and depression may be alleviated through reducing negative coping and increasing perceived social support.