Objective To explore the mediating role of self-esteem in optimism and suicidal risks,and the moderate effect of life events in optimism,suicidal risk and self-esteem.Methods 1 750 college students were surveyed with the life orientation test-revised (LOT-R),the suicidal behaviors questionnaire-revised (SBQ-R),rosenberg self-esteem scale(SES) and adolescent self-rating life events check list (ASLEC).Results The total scores of SBQ-R,LOT-R,SES and ASLEC of college students were (4.78±2.10),(23.17±3.22),(29.58±4.43)and (36.54±21.73).Optimism scores were negatively correlated with suicidal risk scores(r=-0.23,P＜0.01),optimism scores were positively correlated with self-esteem (r=0.50,P＜0.01).Scores of self-esteem scales were negatively correlated with suicidal risk scores(r=-0.35,P＜0.01).A structure equation model consists of optimism,self-esteem,suicidal risk and it had a better degree of fitting (the path form optimism to suicidal risk were r =-0.05,P＜0.05,RMSEA =0.05,GFI =0.90,NFI =0.92,CFI =0.93).The relationship between optimism and suicide risk were mediated by self-esteem(P＜0.01),which accounted for 76％of the total effects.The life events' moderating effects between self-esteem and suicide risk were significant(P＜0.01).Conclusion Self-esteem has a significant correlation with optimism and suicidal behaviors,self-esteem plays an intermediary role between optimism and suicidal behaviors,and life events play an regulation role between self-esteem and suicidal behaviors.