PURPOSE: To determine the status of depression and its key influencing factors among Chinese older adults in different living situations. METHOD: Data of 7,092 older adults were obtained from the China Health and Retirement Longitudinal Survey. This study analyzed key variables influencing depressive symptoms using random forest modeling and logistic regression. RESULTS: The prevalence of depressive symptoms in older adults is 33.2%, with the highest prevalence of depression in older adults living alone (41.2%). Cognitive functioning and life satisfaction are psychological factors that affect older adults' mental health, whereas self-rated health and child relationship satisfaction are biological and social factors affecting their mental health, respectively. Furthermore, self-rated pain and limitations in activities of daily living were identified as risk factors for their mental health. Key factors affecting older adults' mental health differ between living situations. CONCLUSION: Key factors of depressive symptoms in older adults differ across living situations, providing a priority and reference for differential prevention and precise intervention of depressive symptoms to promote a healthy aging process. Results of the current study may help clinicians better understand the pathogenesis of depression in older adults, guide clinical diagnosis and treatment, and develop individualized depression prevention and management strategies. [