Objective: To explore whether social support has a moderating effect on the relationship between negative emotions including depression, anxiety, stress with suicidal behaviors, and to provide reference for the suicide prevention among college students. Methods: Three universities were selected in Qinghai, Ningxia and Xinjiang province, and 4 893 college students were selected using cluster sampling method. The Social Support Scale, Depression-Anxiety-Stress Scale(DASS) and Suicidal Behavior Questionnaire-Revised self-evaluation questionnaires were used to collect data. Hierarchical linear regression model was employed to explore the moderating effect of social support. Results: A total of 4 893 college students completed full questionnaires and included in the final analysis. Among them, 738(15.08%) were under high risk of suicidal behaviors. The regression model showed that DASS score was positively associated with suicidal behavior (β=0.31, P<0.01), and social support was negatively associated with suicidal behavior (β=-0.08, P<0.01); Additionally, the interaction between social support and DASS negatively correlated with suicidal behavior (β=-0.05, P<0.01). Conclusion Social support may have buffering effects on the relationship between negative emotions (depression, anxiety and stress) and suicidal behaviors.