Objective To explore the trajectores of cognitive function of the elderly over time, and analyze the impact of lifestyle on cognitive function. Methods Four set of longitudinal follow-up data from 2008 to 2018 in the Chinese Longitudinal Healthy Longevity Survey (CLHLS) were used.In the sample of 1 473 elderly people aged 65 and above with complete information, latent class growth modeling was used to identify the heterogeneous development trajectories of cognitive function, and generalized additive mixed modeling (GAMM) was used to analyze the impact of different lifestyles on cognitive function of the elderly. Results The scores of cognitive function of the elderly in 4 longitudinal follow-ups decreased gradually.The heterogeneous development track of cognitive function of the elderly can be divided into 3 trajectories, namely, good cognitive group (80.4%), cognitive improvement group (10.3%) and cognitive deterioration group (9.2%).GAMM results showed that gender, age, education level, economic status, vegetable intake, fruit intake, nut intake, housework, reading books and reading newspapers, watching TV or listening to the radio had significant impact on cognitive function of the elderly (P＜0.05 for all). Conclusion Cognitive function of the elderly shows a downward trend as time goes by.There are three kinds of development trajectories of their cognitive function changes.We should focus on the elderly with low education, poor economic conditions and lifestyle problems, actively carry out entertainment and sports activities, and provide healthy diet guidance to delay the deterioration of cognitive function in the elderly.