The purpose of this research-in-progress paper is to explore factors affecting users’ participation in microblogging. Based on literature review and the stimulus-organism-response (S-O-R) framework, a conceptual model is proposed to depict the relationships between the features of micro-blogging services and users’ behavior. Specifically, the features of micro-blogs such as subscription, broadcasting and interoperability are believed to influence users’ perception of interactivity, which is considered as a key factor affecting individuals’ sense of telepresence and social presence, and eventually affect individuals’ participation in microblogging. The future research and expected contribution is discussed at the end.