Objectives: To explore the relationship between depression and suicidal ideation of freshmen, as well as the intermediary of opinion to suicide behavior between them. Methods: A total of 1 395 freshmen (517 males and 878 females) from two universities were selected. They were assessed with the symptom checklist 90 (SCL-90) for depression symptom, questionnaire of suicide attitude (QSA) for opinion to suicide behavior, and questionnaire for suicidal ideation. Results: Depression symptom scores in freshmen were positively correlated with suicidal ideation scores (r=0.091, P ≤ 0.001), while the opinion to suicide behavior scores were negatively correlated with depression symptom scores and suicidal ideation scores (r=-0.309~-0.100, P < 0.001). In addition, the opinion to suicide behavior was intermediary between the depression and suicidal ideation of freshmen. Conclusion: The opinion to suicide behavior can partly buffer the effect of depression of freshmen on their suicidal ideation.