Theodore Dreiser is now regarded as one of the pre-eminent American realistic novelists of the first half of the twentieth century, an anatomist of the American Dream. In his great work An American Tragedy, Dreiser exposes and criticizes mercilessly the corruption and black side of American society. The disillusionment of the American Dream is an important theme of the fiction. This paper illustrates “An American Tragedy” is the reflection of disillusionment of the American Dream in the perspectives of the tragedy of a mortal, the tragedy of American society, and the tragedy of the American Dream. Theodore Dreiser is now as one of the pre-eminent American realistic novelists of the first half of the twentieth century, an anatomist of the American Dream. In his great work An American Tragedy, Dreiser exposes and criticizes mercilessly the corruption and black side of American paper. The disillusionment of the American Dream is an important theme of the fiction. This paper shows “An American Tragedy ” is the reflection of disillusionment of the American Dream in the perspectives of the tragedy of a mortal, the tragedy of American society, and the tragedy of the American Dream.