This political communication research analyzed the impact of digital media on public opinion. This is a qualitative and interpretive study that observes how users participate in political discussions through social media. The survey aims to analyze the opinions and expressions surrounding the proposed theme, using case study as a research strategy, and adopting methods such as frame methods and qualitative content analysis. Starting from this concept, question are raised: In the 2019 Hong Kong protests, existed a Spiral of silence phenomenon on social media? This research has important scientific and innovative contributions. In order to understand these issue, based on the Spiral of silence hypothesis, this study manually analyzed 76 posts on the Facebook website of the South China Morning Post and 2,000 public comments. The development of the theory Spiral of silence (Noelle-Neumann, 1974) pointed out that people retain their opinions when they think that the climate of opinion is contrary to their own opinions, and this silence will increase over time. The analysis of this research shows that on the Facebook platform, a minority of opinion holders tend to retain their opinions, but as time goes by, a minority of determined people begin to express their opinions, which shows an intermittent Spiral of silence in time, probably motivated by factors exogenous to the observed discussion environment. The research aims to contribute to the advancement of the environment for public political participation on the current social media, through the study of the media environment and media content. The background of the research is the Hong Kong Anti-Extradition Law Amendment Bill movement. This special background has innovative significance, enriching empirical research on Eastern countries, and providing new ideas for non-campaigns political participation research.