Objective To explore potential association between sedentary time and the risk of all-cause mortality and cardiovascular disease(CVD)in Chinese population using data from the Prospective Urban Rural Epidemiology(PURE-China)cohort study.Methods Baseline data were collected,from 2022 standardized questionnaires and physical examinations,with follow-up until August 31,2022.The primary endpoints were all-cause mortality and cardiovascular events(non-fatal myocardial infarction,stroke or heart failure).Multivariable Cox shared frailty model was used to analyze the association between sedentary time and the risks of all-cause mortality and CVD in the target population,and to compare differences across subgroups based on gender,age and geographic location.Results A total of 47 931 participants were recruited,and 43 367 were included in the final analysis.Over a me-dian follow-up of 11.9±3.0 years,2 277 participants experienced all-cause mortality,3 551 experienced cardiovas-cular events.The Cox model indicated that,compared to individuals with less than 4 h of sedentary time per day,those with 6-8 h had a 23％increased in risk of all-cause mortality(HR=1.23,95％CI:1.06-1.44)and an 18％increased risk of CVD(HR=1.18,95％CI:1.04-1.33).For individuals with more than 8 h of sedentary time,the risk increased by 50％for all-cause mortality(HR=1.50,95％CI:1.16-1.94)and 44％for CVD(HR=1.44,95％CI:1.16-1.79).These associations were more pronounced in men and individuals aged 50 years and older.Conclusions Sedentary behavior is associated with an increased risk of all-cause mortality and cardiovascular disease in Chinese population,especially in the population with sedentary time of 6 hrs or more per day.Reducing sedentary time and increasing physical activity is an important strategy to mitigate the disease burden of cardiovascular disease and premature death.