The aging of the population has become gradually deepened in China. The aged care servicessystem should focus on the disabled elders. However，past studies have not yet explored in - depth aboutdepression among the elderly caused by disability. The study aims to estimate the impact of disability ondepression among elderly population by the Instrumental Activity of Daily Living based on CFPS2018 surveydata and analyze its heterogeneity effect. Secondly，the study employs the mediation between personality traitsand cognitive ability. Thirdly，the study analyzes the moderating effect of social support and social participation.The robustness test indicated a significant negative correlation between IADL and depression among the elderly.In addition，three personality traits and mathematical reasoning ability show significant mediating effects. Theregional and demographic factors show significant heterogeneity between East and West，gender，educationlevel and age. Therefore，this study suggests improving the assessment and monitoring system for disability andcognition among elderly population，setting up the early warning mechanism of mental health for focus groups ofparticular personality traits and cognition，and improving the construction of mental health medical services inthe primary public health system. This study also recommends that the government utilizes long - term careinsurance，which plays a vital role in the mental health of disabled elders at the institutional level，while alsopromotes Smart Senior Care services to enhance the social participation of the elderly.