Objective To explore the moderating or mediating effects of life-meaning between optimism and suicide risk in undergraduates.Methods A total of 1310 college students from one Chinese university completed a survey that included Suicidal Behaviors Questionnaire-Revised (SBQ-R),the Life Orientation Test-Revised (LOT-R) and the Chinese meaning in life questionnaire (C-MLQ).Results The total scores of SBQ-R,LOT-R and C-MLQ of undergraduate were (5.04 ± 2.28),(11.22 ± 2.07) and (37.22 ± 5.22),respectively.Optimism had significant negative correlation with suicide risk (r =-0.22,P ＜ 0.01),and positive correlation with life-meaning (r=0.28,P＜0.01).Life-meaning had significant negative correlation with suicide risk (r=-0.18,P＜0.01).The life-meaning's moderating effects between optimism and suicide risk were not significant(P ＞ 0.05),while the relationship between optimism and suicide risk was mediated by life-meaning,and the mediating effect was 0.07,which accounted for 17％ of the total effects.Conclusion Life-meaning doesnt morderating effect,but partially mediates the relationship between optimism and suicide risk.