With the growing pervasive use of smartphone, people are becoming increasingly dependent on their mobile social media for real-time information obtainment and social connection. However, the addictive use of social media has drawn little attention in IS research and the very few extant studies tend to merely adopt conceptualizing approaches such as content analysis, statistic descriptions, and general measurement. Given that there is little theory-driven empirical research on the underlying process of addictive use of social media, this study focuses on understanding the process of addiction (using microblogging as an example) as well as identifying the role of relevant enacting variables. Drawing from the stimulus-organism-response model of behavior, this study proposes a research model that explains the development of addictive use of microblog. In particular, we focus on the role of media characteristics in the provision of technological stimulus which may have a bearing on the resulting additive usage behaviour. An online survey was conducted to empirically validate the theoretical model. The results indicate that microblog addiction is a repetitive response to avoid internal negative affect, rather than to strengthen positive affect. The media characteristics of microblog (i.e., information scope, feedback mechanism, and convenience to access) that satisfy users’ pleasurable media experience are found to exert an important effect on both positive and negative affect. In addition, individuals’ social psychological characteristic (i.e., deficient self-regulation) was found to play a critical role in the development of addiction behavior. Keywords: Media characteristics, problematic mobile phone use, addiction, positive affect, negative affect, deficient self-regulation, microblog, social media