〔Abstract〕 To explore the relationship between negative life events and depression severity in adolescent patients with depressive disorder, as well as the chain mediating role of insomnia symptoms and quality of life. Methods From January 2021 to December 2022, 374 outpatient patients and hospitalized patients with adolescent depressive disorders were enrolled. The Adolescent Life Event Scale (ASLEC), the Insomnia Severity Index (ISI), the World Health Organization Quality of Life Questionnaire Short Form (WHOQOL-BREF), and the Center for Epidemiology Depression Scale (CES-D) were used to evaluate the negative life event situation,insomnia symptoms, quality of life level and depression severity of the subjects, respectively. In addition, the PROCESS 4.0 macroprogram was used to analyze the chain mediating effect of insomnia symptoms and quality of life between negative life events and depression severity in patients with adolescent depressive disorder. Results The results of correlation analysis showed that there was a significant correlation between negative life events and insomnia symptoms, quality of life, and depression severity (all P<0.05). In addition, the results of chain mediation showed that negative life events had a significant direct effect on depression severity, with an effect size of 0.12 (P<0.001). Insomnia symptoms and quality of life played a mediating role in he relationship between negative life events and depression severity in patients with adolescent depressive disorders, with indirect effect sizes of 0.061 (95%CI: 0.040-0.087) and 0.100 (95%CI:0.065-0.136), respectively. It could also play a chain mediation role, and the effect size was 0.043 (95%CI: 0.026-0.063). Conclusion Negative life events experienced by patients with adolescent depressive disorder not only directly affect the severity of depressive symptoms, but may also indirectly exacerbate depression through insomnia symptoms and quality of life.