From the Arab Spring to the Me Too Movement, social media has shown tremendous power to mobilize collective actions in democratic and authoritarian countries. China has the world’s largest and most active social network market (Statista, 2019). An emergent online discursive space in China has therefore aroused more and more attention. In current literature, social media platforms’ role in is an imperative topic embedded in both new media studies and social movement studies. Despite previous research has proven the implications of social media (for example Facebook, Twitter, and Microblog) for empowerment, few scholars have paid attention to social mobilization initiated through WeChat, which has become the most popular social media application in China. To provide insight into the role of social media in protest mobilization, I focus on anti-incineration campaigns based on WeChat platform and attempt to explore whether and to what extent can WeChat provide an opportunity for Chinese activists to enable them to challenge the established order in incineration field (Fligstein and McAdam, 2011, 2012)? To answer this question, I identified 12 anti-incineration subscription accounts and exported 556 texts related to waste incineration posted on these accounts. Based on discourse analysis approach, Nvivo was applied to code and examine these anti-incineration posts. Emphasizing structure and agency (Giddens, 1984), my study focuses on two concerns: objective technical conditions and subjective construction process of online anti-incineration mobilization. In this contribution, the first axis presents the efficiency and interactivity of WeChat as a horizontal communication tool. WeChat creates a space for user-generated content in which operators of subscription accounts are allowed to send posts directly to subscribers. Platform architecture of WeChat also provides point-to-point (through “Send to Chat”), point-to-multipoint (by “Send to Group Chat”), and scattershot (via “Share with All in Moment”) dissemination services. Given the high-intensity use, WeChat serves a good tool that enables activists to construct an online community of protest. The second axis shows the social construction process of waste incineration issue. Juristic rhetoric, scientific rhetoric, and ecological rhetoric are widely used and considered as discursive opportunity structures. Diagnostic framing (Snow and Benford, 1988, 1992) mainly refers to technical defects, environmental risks, illegal land acquisition, the lack of information, and insufficient public participation. Accordingly, prognostic framing (Snow and Benford, 1988, 1992) involves technology upgrade, monitor and management, relocation of incineration plants, information disclosure, public participation, and other policy changes. In sum, this study provides empirical evidence to enrich existing understanding of the formative role of social media in disseminating controversial topics and methods used by activists to present controversies.