Plagiarism has been an increasingly serious problem on campus. Many college students use others' ideas without reasonably stating the sources. Even some professors are discovered to have borrowed passages from the works of others. Undoubtedly plagiarism has much bad effect. First, those whose works have been plagiarized suffer losses because their efforts were not duly recognized. Second, those who plagiarize also endure great mental pressures. Plagiarism may have brought them something they need for the moment, but they are always in a fear that someday their plagiarism may be disclosed, and then their career may be totally destroyed. Finally, plagiarism brings negative impact on the ordinary people. They may lose their faith in the academic field and no longer believe in the saying "Honesty is the best policy." To avoid plagiarism, both prevention and correction are needed. For prevention, all people should be taught lessons on the various forms of plagiarism. For correction, severe punishment is called for when plagiarism is discovered.