<p>During sudden natural disasters, people participated in online discussions based on different behavioral motivations, thus forming a unique online public opinion on earthquakes. Online public discourse accompanying an earthquake event introduces a risk to public opinion, where rumors can quickly incite public panic. This paper begins by examining the four factors of earthquake online public opinion. It constructs a public opinion risk evaluation index system that incorporates earthquakes, social media users (netizens), media, and the government. Secondly, the indicators are further selected through correlation analysis and principal component analysis, and after rationality testing, a more scientific and complete risk evaluation index system is obtained. Thirdly, the entropy weight method is employed to determine the weights of the index system. Finally, this paper takes the Mwg 5.7 earthquake in Yibin, China, as an example. The public opinion risk values for the online public opinion burst period, spreading period, and dissipation period are calculated, respectively, and the overall public opinion risk value is determined. The risks are graded, and the corresponding emergency countermeasures are put forward. Through research, we found that the public opinion risk assessment system established in this paper effectively analyzes and evaluates earthquake online public opinion. It provides valuable insights for government agencies (such as emergency management, public relations, and earthquake bureaus) in responding to earthquake online public opinion, helping to deliver accurate information and correct any misinformation that may spread, thus enabling more effective earthquake relief efforts and post-disaster reconstruction.</p>