In Li Mao Dressing as a Prince, Chang Yuan played two roles. He was both a prisoner of Li Mao and a prince of the dynasty. He needs to switch back and forth between the two roles, which tests Chang Yuan's acting skills. Although both Li Mao and Prince Chang Yuan appeared, they were not alone in the play. Li Mao is Li Mao, and the prince is the prince. They look like a coincidence.

Li Mao is a young policeman. He is very affectionate with the rich girl Yang, but his father-in-law despises him. In order to get their approval, Li Mao decided to do something big. He overheard the ministers and county magistrate asking the prince to go to the theatre, so Li Mao changed his teahouse into a theater. What he didn't know was that Shangshu and the county magistrate wanted to take this opportunity to assassinate the prince.

Later, Li Mao was told that the prince could not leave the palace during the theatre, so he sneaked into the prince's mansion and tried to take him out. Who knows that the prince looks exactly like him, and the prince wants to go out of the palace for fun. He simply exchanged identities with Li Mao, and then changed back after the play. During this time, Li Mao felt the taste of being a prince, and the prince also tasted the taste of people's misery. He especially likes Yang's potherb porridge and says Li Maoshen.

On the day when the Prince went to the theatre, Li Mao suddenly understood the conspiracy of Shangshu. In order to protect the prince, Li Mao was in deep danger. Finally, Shangshu died and Li Mao survived.

Li Mao was raised by the emperor for his meritorious service in saving the prince, but he didn't want it. The emperor worshipped him as a brother. The prince became Li Mao's nephew, and everyone was very happy. Li Mao was praised by her parents-in-law and assured to give her daughter to him. Yang always wanted a child, and Li Mao gave it to her. They have the crystallization of love and a happy family. The prince felt the affection from Li Mao and learned the emperor's good intentions, so he decided.