Abstract: Objective: To explore the relationship between depression and non-suicidal self-injury (NSSI) and the mediating effect of social support between depression and NSSI among medical students.Methods: Guangxi Medical University was selected as the research site, and a total of 859 medical students were recruited in the study to complete the self-designed General Situation Questionnaire, Ottawa Self-injury Inventory (OSI), Center for Epidemiologic Studies Depression Scale (CESD) and Perceived Social Support Scale (PSSS).Results: The detection rate of NSSI among medical students of Guangxi Medical universities was 15.13% (130/859).The CESD scores were positively correlated with NSSI scores (r=0.425, P< 0.01) and negatively correlated with PSSS scores (r=-0.524, P< 0.01).The PSSS scores and the three dimensions (friend support, family support and other support) scores were negatively correlated with NSSI scores (r=-0.33, -0.27, -0.31 and-0.33, all P< 0.01).Social support played a partial role in mediating the relationship between depression and NSSI among medical students.The proportion of mediating effect was 18.75%.Conclusion: Depression may drive the occurrence of NSSI among medical students, but this process can be buffered by mediating variables of social support.Good social support can help reduce the risk of NSSI among medical students with depression problems.