The present study, drawing on a corpus-assisted three-dimensional discourse framework, examines China’s national image in terms of keywords, collocations and concordances in a self-built corpora of U.S. mainstream media reports on Beijing Winter Olympics, attempting at the motivations for constructing China’s national image by U.S. Mainstream Media. It is found that the U.S. mainstream media constructed a complex and negative image of China around such topics as “Winter Olympics”, “human rights”, “democracy” and “foreign relations”. As the American ideological apparatus, the U.S. media’s negative construction of China’s image deviates from the objectivity and impartiality of news, which is dictated by American national interests.