Social media have become popular channels for sharing and discussing science issues. Drawing from the classic communication theory, Public Arena Model, this paper examines how issue entrepreneurs influenced the Chinese public's cognition of GMO, especially the role of celebrities and scientists in controversial science communication. To answer this question, we used the structural topic modeling method to examine public discussion about GMO on a popular Q&A site in China (Zhihu) from 2014 to 2019 (N=40,101). In study 1, we investigated what the major themes of public discourse are about GMO and the evolution of these themes in general. In study 2, we investigated public discourse in a more specific context, an iconic event in China's GMO history, a debate between a TV celebrity and a scientist, to examine how two major issue entrepreneurs influenced what and how the public deliberated GMO. We found that the issue entrepreneurs' debate increased public discussion on the ‘science communication’ aspect of GMO yet decreased public discussion on the ‘science’ of GMO. Supporters of different entrepreneurs are divided in their attitudes and rhetoric toward GMO. These findings shed new light on how social media is a digital embodiment of the public arena where public deliberation about controversial science occur and evolve.