Background: A singular ecological risk factor did not accurately reflect the reality of adolescents' lives and could not fully elucidate the developmental mechanisms of adolescent suicidal ideation. The cumulative effect of multiple ecological risk factors (which may interact synergistically) could have provided a more comprehensive understanding of the developmental mechanism of adolescent suicidal ideation from a systemic perspective. Objective: Based on the ecosystem theory, this study aimed to explore the relationship between cumulative ecological risk and adolescent suicidal ideation, and the moderating effect of meaning in life. Method: A sample of 16,508 adolescents completed the Cumulative Ecological Risk Questionnaire, the Meaning in Life Questionnaire, and the Depressive Symptom Index Suicidality Subscale. Results: The results showed that: (1) Cumulative ecological risk was positively correlated with suicidal ideation, and meaning in life was negatively correlated with suicidal ideation; (2) Cumulative ecological risk could predict adolescent suicidal ideation, showing an 'exacerbation model': wherein the already positive association between an individual risk factor and suicidal ideation was worsened by the simultaneous presence of other risks; (3) The protective effect of meaning in life on adolescent suicidal ideation decreased with the increase of cumulative ecological risk, presenting a 'protective-reactive' moderating model. Conclusions: The results revealed that once the capacity of ecological risk factors exceeded the capacity of protective resources, meaning in life alone was no longer sufficient as a protective resource. Instead, it would be necessary to also intervene in ecological risks to improve individual development.