The paper studies the influence of China social transformation risk to online public opinion using empirical research method. Through correlation analysis between the social transformation risk items and numbers of important online public opinion events during 1998-2009, we discover that social transformation risk and economic transformation risk significantly affect the occurrence of important online public opinion events; the political transformation risk to some extent is related to the occurrence of important online public opinion events in China. Meanwhile, the more intense of the relationship among social communities, the more fragile of social communities' bearing capacity; the stronger of social unsafe feeling; the more the online public opinion events would be. It refers that online public opinion in China is directly influenced by social transformation, and online public opinion is the mirror of actual social risk on virtual internet society. <<