Abstract： Objective To investigate the associations between lifestyle factors and social network and cognitive impairment among the elderly in three communities in China.Methods From November 2017 to May 2018,1 200 elderly individuals were selected from three Chinese communities (Beijing,Hefei,and Lanzhou) using a random cluster sampling method.Data were collected on lifestyle,social network,and cognition.A conditional logistic regression analysis was conducted to identify the associations between lifestyle and social network and cognitive impairment.Results A total 1 115 participants (92.9％) were administered both social network and cognition questionnaires.After adjustment by age,sex,education,marital status,health,and living status,only low participation in physical activity was found to be associated with cognitive impairment (OR=0.65,95％ CI=0.45-0.93,P=0.019).A larger social network (OR=0.50,95％ CI=0.29-0.85,P=0.010),especially more friends (0R=0.44,95％ CI=0.29-0.65,P＜0.001),may decrease the risk of cognitive impairment.The interactions between lifestyle factors and social network were not associated with cognitive impairment.Conclusion Our findings suggest that larger social networks and physical activity are associated with cognitive function among the elderly.Identification and intervention of risk factors are crucial in the delay and prevention of cognitive impairment and the improvement of quality of life among the elderly.