Emotion and story are in conflict, and most of them promote the development of the plot with emotional entanglements and complex relationships. Contradictory duet is the most dynamic vocal genre in the whole play. In addition, the climax of the opera also uses contradictory singing, which is used in the final duet of The Marriage of Figaro. The ending of the second act mentioned above is typical. When the role conflict broke out, the author used the method of raising the voice step by step to render the plot. This duet consists of many forms, from duet to quartet, from the earl's suspicion that there is a man in his wife's room to the appearance of Susanna; Then, Mascelina, Bacelo and Basilio went on stage, and the performances of different roles were treated differently in the interpretation of contradictions. The expression of emotions and the acceleration of rhythm pave the way for the further development of the plot.