Li Yu first put forward the structural principle, and at the same time put forward a whole set of theories such as "conception", "thread reduction" and "sewing needle", all of which were formed in view of the shortcomings in the opera stage at that time. Li Yu advocated strict structure, compact plot and tight organization, which not only had high theoretical value at that time, but also had strong artistic practical significance today.

In terms of language, he thinks that opera is a desk work written for the audience rather than for people, so it should be given the characteristics of stage art. Under this principle, he puts forward that Wen Qu is superficial, emphasizes machine interest and avoids floating and blocking; Bai Bin wants to be simple, saying that a person is like a person and must not be the same; Noble, sonorous and a series of original opinions.

Speaking of the theme, Li Yu believes that innovation is the most important thing, and the first point is to go white. Since the script is called legend, it is because it is strange. If it is spread without being seen, it must not follow suit. Li Yu also said a lot of pertinent words to the director and performance.

The main content of Li Yu's theory of traditional Chinese opera structure.

(1) Li Yu broke through the idea that the previous generation of lyrics emphasized the use of words and melody, emphasized the importance of structure, and thought that words served the structure.

(2) In the history of China's classical drama theory, Li Yu first put forward the viewpoint of "structure comes first", pointing out that playwrights should first carefully design the structure of their works in the process of conceiving their works.

(3) Li Yu systematically expounded the specific principles that should be followed in the structure of traditional Chinese opera works, and put forward a set of complete ideas, such as "setting the main brain", "reducing clues" and "strictly sewing needles".

(4) "main brain" contains two closely related meanings, one is roughly equivalent to today's central idea or creative motivation; Second, we should closely focus on the central idea and choose a central figure and central event as the backbone of the structure, so as to express the central idea more intensively.

(5) Li Yu's theory that "expressing one's original intention" is the central issue in the conception of opera creation is in line with the law of opera creation.