This study examined the pattern of online public opinion change in China by investigating the top one hit blog and its following commentaries of every day from July 2009 to March 2012 on a famous Chinese website, and then discussed potential factors that affected the formation of online public opinion. The extent of freedom of online public opinion during this period presented regular fluctuations. Whether criticisms were registered by commentators was influenced by four factors. First and most important, the negative tone of bloggers increased criticism and the positive tone decreased criticism, which shows that the news that flows from the media to the public is amplified and interpreted by influential bloggers according to the two-step flow theory. Second, while national and local events had no effect, international news events decreased criticism because the public strongly supported the Chinese government. This was as important as the first factor. Third, the negative tone of events discussed in blogs increased criticism, which means that the mass media did have some direct influence through negative but not positive events. And fourth, when the government censored blogs and commentaries, the public shied away from criticism because their posts would probably be removed.