The development of watchdog journalism is a part of media reform and political democratization in China during the past 30 years. This study explores the transformations of "public opinion supervision" in China from a perspective of discourse analysis by analyzing the news reports that won the first-class prize in Chinese Journalism Prize from 1979 to 2006. The analyses trace a shift of supervision subject (from media to the public) and professionalization of discursive technology in news reporting. It also shows that negotiations over public opinion supervision between the party-state and the media with increasing autonomy have become increasingly legitimate. Although the established regime of public opinion supervision has not had a fundamental change under the control of CCP, the discursive practices of public opinion supervision reflect and reconstruct the power relations between the media and party-state in China.