Abstract: In recent years， online public opinion has gradually changed the traditional political process. Cyberspace becomes an important platform for deliberation. The irrationality of online public opinion has always been the focus of the debate on whether the network can realize the deliberative democracy. Taking the “Shandong Illegal Vaccine Case” as an example， this paper uses content analysis and text analysis methods to grasp the actual situation of deliberation and public rationality in online public opinion events from the two dimensions of political process and network platform. With the deepening of the political process and the enhancement of network platform's institutionalization， the public rationality of netizens has increased. In the deliberation of online public opinion events， positive government responses and good network platforms are conducive to the realization of public rationality of netizens.

Key words: online platform, online public opinion, online deliberation, public rationality