The structure pairs of part-of-speech pairs in contemporary couplets are a further explanation and summary of the characteristics of category-finding pairs of ancient words. They were more flexible in ancient times and were refined with more established examples after Chinese grammar. There are no good couplets before Chinese grammar. Chinese grammar should follow the usual usage habits. The language can make people understand the meaning, read smoothly, and conform to the rules of style. It is a matter of theoretical research to keep the theory as far as possible and to deepen the research, but the actual writing only needs to follow the prevailing practices.