“Social media” appear as a confusing term in the research area, the disadvantage has increased the difficultly of social media effect research. This thesis aims to define a welldenoted academic definition for the term “social media”. Further step is to explore its effect on traditional media and netizens’ offline sociability. Whether social media use will be displaced or reinforced the time spend on traditional media and netizen’s fact to face interaction with others is the key research question for investigation. Data collected from random telephone survey in Macao shows that social media use time displacement effect is a mixed impact in accordance with different media characteristics. There is displacement result such as frequent SNS user is likely to spend less time on watching TV. Reinforcement result such as frequent RSS user is likely to spend more time on more newspaper reading, as well as frequent BBS/Forum user tend to spend more time on radio listening. The new dimension of social media use: diversity of media use shows null effect towards all the traditional media and netizens’ sociability. Similarly, the null effect of time displacement on netizens’ sociability has proven that offline interaction may bot be a behavior that can be easily displaced by online social interaction. keywords: social media, traditional media, netizen’s sociability, time displacement effect, functional equivalence, many to many communication mode