Abstract: Tomes Hardy is one of the most prominent British novelists and poets in the Victorian period. The Mayor of Casterbridge is among his masterpieces of character and environment novels, the background of which is set in Wessex. As the theoretical basis of modern structuralist linguistics, binary position principle is widely used in literary creation and literary criticism. With this principle, an analysis of three dominant pairs of binary opposition, namely man's will and tragic fate, male and female, as well as agricultural and industrial civilization respectively is made to expound the tragic thoughts embodied in the novel. Thus a conclusion can be drawn that Hardy is good at applying the principle of binary opposition to highlight the tragic thought of the novel and enhance the tragic atmosphere.