BackgroundSuicide among adolescents has become a serious public health issue， with suicidal ideation serving as a necessary precursor to suicide attempts and death. Previous research suggests that campus exclusion， depression， and psychological resilience are closely associated with the development of suicidal ideation in individuals. However， there is a lack of longitudinal research to deeply explore the relationship between each influencing factor and suicidal ideation. ObjectiveTo explore the impact of campus exclusion on suicidal ideation among adolescents， as well as the mediating role of depression and the moderating role of resilience， so as to provide references for formulating strategies for preventing and intervening in adolescent suicide. MethodsAUsing a longitudinal research design， in November 2023， 1 226 students from 21 classes （4 classes per grade in junior high school and 3 classes per grade in senior high school） from a junior high school and a senior high school in a certain area of Shandong Province were selected as the research subjects. The Ostracism Experience Scale for Adolescents （OES-A）， the Patients' Health Questionnaire Depression Scale-9 item （PHQ-9）， and the Resilience Scale for Chinese Adolescents （RSCA） were used for assessment. The PHQ-9 suicide ideation item was evaluated again three months after the baseline survey （the two suicide ideation evaluations were respectively denoted as T1 and T2 respectively. Spearman correlation analysis was used to examine the relationships among scale scores. Model 4 and model 59 in the SPSS macro program Process 4.2 were used to test the mediating effect of depression between school exclusion and suicide ideation， as well as the moderating effect of psychological resilience on the three paths. ResultsCorrelation analysis showed that OES-A score was positively correlated with PHQ-9 score and suicidal ideation item score （T2）， and PHQ-9 score was also positively correlated with suicidal ideation item score （T2） （r=0.361， 0.292， 0.508， P<0.01）. RSCA score was negatively correlated with OES-A， PHQ-9， and suicidal ideation （T2） scores （r=-0.500， -0.676， -0.459， P<0.01）. Campus exclusion positively predicted suicidal ideation （T2） and depression （β=0.081， 0.281， P<0.01）， while depression positively predicted suicidal ideation （T2） （β=0.108， P<0.01）. The mediation analysis revealed an effect size of 0.030 （95% CI： 0.019~0.043， P<0.01）， accounting for 37.35% of the total effect. Psychological resilience moderated the relationships between campus exclusion and depression， campus exclusion and suicidal ideation （T2）， and depression and suicidal ideation （T2） （β=-0.059， -0.049， -0.062， P<0.01）. ConclusionA moderated mediation model exists among campus exclusion， depression， resilience， and adolescent's suicidal ideation. Psychological resilience moderates the associations between campus exclusion， depression and suicidal ideation across all three paths. ［Funded by Beijing Municipal Health Commission Clinical Research Excellence Program， （number， BRWEP2024W072130101）；Beijing Municipal Hospital Management Center Summit Program， （number， DFL20221701）］