Functional disability is a widespread challenge faced by the older population in China, where those with functional disabilities demand greater healthcare and geriatric services. This study performs a longitudinal analysis examining the effects of physiological conditions, intra-, and extra-individual factors, and life-course socioeconomic status risk factors on the disability levels and change rates of functional disability trajectories in old age. Data for this study came from the four waves of the China Health and Retirement Longitudinal Survey. A latent growth model was used to analyze the functional disability of 5044 older adults aged 60 and over in 2011 who survived to 2018. Pathologies are closely associated with functional disability trajectories, and higher numbers of comorbidities relate to more disabilities. Risk factors and intra- and extra-individual factors affect functional disability trajectories and work through independent and shared mechanisms. The effects of risk factors can be traced to childhood conditions, and higher childhood and adulthood socioeconomic status is related to fewer functional disabilities. Functional disability trajectories are dynamic processes related to pathologies, intra-, and extra-individual factors, and life-course risk factors, and thus prevention and control measures should focus on both childhood and adulthood. Promoting working in later life and improving childhood socioeconomic statusdeserve prompt attention. Geriatr Gerontol Int 2023; 23: 817-829.