This study examines Diba Expeditions (a series of cross-platform cyber-protests organized by seemingly grass-root Chinese patriots) during the Hong Kong Anti-ELAB protests as an example of cyber-protests. I use a supervised machine learning model to distinguish between Diba and ordinary Facebook users’ comments in a dataset of over three million comments posted on 16 Facebook pages. Sentiment analysis measures the attitudinal changes towards China and the Hong Kong Police in these comments. The difference-in-difference regression models show that the Diba Expeditions are able to amplify the pro-China voices in the targeted pages, especially in the anti-protest ones. This paper is the first to systematically measure the effect of Diba Expeditions. It thus contributes to our knowledge of self-organized Chinese political events on social media and reveals the influence of cyber-protests with no follow-up physical activity.