A green public sphere is important for the free environmental communication in a country. However, this concept is relatively new to the public in China. Here we show that the PM2.5 event in 2011 play an important role in the formation of a green public sphere in China. First, we reviewed the PM2.5 event in China and the basic theory of green public sphere. Next, we investigated the role of the PM2.5 event in the formation of a green public sphere in China. Finally, we concluded that a green public sphere has complicated structures and is multilayered.