Causal/remedy attribution, emotion venting and interests conflict are common in online discussions on public affairs, which are far from democratic deliberation in “public sphere.” In order to understand the characteristics and interaction model of online forum in China, this paper examined online discussions on “mask wearing statue in Peking University” in the weibo accounts of People’s Daily and Sina Pictures based on emotional framing theory. It analyzes how the substantive contents of various discourses interact with emotions these discourses carry. It finds that weibo-sphere acted more like a pressure valve than a public sphere. Emotional criticisms dominated online discussions and emotions spread. Conflict discourses trigger anger and reduce dialogue. This study is useful to emotional framing theory construction, understanding online forum in China and online discussion practice.