In contemporary society，social network has been widely used and is changing the mode of people’s social interaction and social life. From this perspective，based upon the analysis of inter-generational gap of internet usage，this report describes the use of social network by different generations in multiple areas of everyday life. The data of this report come from an online survey which is jointly conducted by the National Survey and Big Data Research Center of Chinese Academy of Social Sciences and Tencent Center for Internet & Society. The main findings of this report can be summaries as “duality of social network”. On the one hand，the structure of social network is characterized by instrumentality which provides instruments in everyday interaction and brings convenience and pleasure and fulfill family commitment. On the other hand，social network is a virtual space of practice，which has changed people’s interaction，lifestyle and values. At the same time，social network has brought anxiety and dilemma to certain extent. This report generates helpful implications for internet studies and sociological research methods，and gives useful policy implications for social governance and improvement of life quality and security.