The social convoy model and the socioemotional selectivity theory，which have been adopted to study the social networks of elderly people in the Western societies，are tested in the Chinese context to shed light on the important factors affecting social isolation of the elderly in China．Employing data from China Longitudinal Aging Social Survey ( CLASS) ，this paper examines the current situation of family and friend isolation of the Chinese elderly，and analyzes the determinants of social isolation using logistic regression models．The results show that ageing increases the risk of friend isolation，but restrain the possibility of family isolation．A comparison of the determinants of family isolation with those of friend isolation suggests that family characteristics are the main predicting factors for the elderly family isolation，while health status is the major determinant of friend isolation of the Chinese elderly.Socioeconomic status，social participation and social environment are also significant influencing factors．