In China, the advent of Weibo, the biggest Chinese microblog platform (launched in 2009), has brought changes to the restrictive communicative environment. Through rapid information dissemination and exchange of opinions online, it creates a public sphere where Chinese netizens exercise media citizenship. Adopting a discursive approach, this study explores the disagreement strategies and their role in public sphere building in Chinese mainstream media editorial comments on Weibo. These disagreement strategies are used to criticize the content of the editorial, attack the trustworthiness and impartiality of the mainstream media, and express negative emotions to the mainstream media. The findings suggested that the online commenting space on Weibo is a public sphere of combined deliberation and liberal individualism.