The "Mao Shi Zhengyi" compiled by the emperor of the Tang Dynasty, Kong Yingda and others, was at an important stage in the history of exegetical studies. It not only inherited the achievements of the Han Confucian classics and the Southern and Northern Dynasties, but also inspired the new classics of the Song Dynasty. In the process of "Mao Shi Zhengyi" interpreting the scriptures, there are quite a few cases of "tong" and "yitong", whichever is related to the interpretation of the scriptures, with a preliminary count of 130. Investigating its nature, it could be analyzed as: "exegetical terms" to explain the phonetic and meaning relationship between the characters to be explained and the characters to be explained, and the terms used to explain meanings. According to its usage and connotation, it could be divided into five categories: "Synonyms with common meanings and different meanings", "Phonetic loan character.", "Phrase and sentence patterns", "Mutual feet and opposite texts", "Poetry and textual context" ". The conclusion points out that when the "tong" and "yitong" of "Mao Shi Zhengyi" are used as "exegetical terms", they have two characteristics: the same exegetical term expresses the ambiguity of multiple concepts and regulations; and the same exegetical concept and regulations, but the vagueness expressed by multiple exegetical terms. "Distinguish between essays and general prose" is the "exegesis of rectifications." The purpose of name argumentation is to explain the "speech meaning" (specific meaning) of words in the context; the "linguistic meaning" (general meaning) of words It is the basis for it to derive specific meanings. This is also one of the major principles of the exegetical terms "tong" and "yitong" used in "Mao Shi Zhengyi". And when "tong" and "yitong" are used to explain meaning and principles, from their use, we can know the two exegetical principles of "Mao Shi Zhengyi": First, identify the reasons for the similarities between different theories, and place them in the same way. Context, where the interpretations can be interlinked, rather than avoiding the contradictions between the two theories from a "universal" point of view; second, when "Mao Shi Zhengyi" interprets the Shijing, the “Preface" of he poems, the chapters, and the sentences are regarded as an indivisible whole.