Edward Sapir published Language in 1921. This book includes both the language external research, the research on the languagerelated culture, and the language internal research, the research on language concept system. In the grammatical analysis, Edward Sapir places persistent emphasis on languages social and psychological essence. This perspective is not only reflected in the popular ″SapirWhorf Hypothesis″ but also in Sapirs grammatical research. The fifth chapter Form in Language: Grammatical Concepts presents Sapirs unique grammatical analysis which is conceptcentered and meaning based. It is unique in that Sapir categorizes different language elements according to the various concepts conveyed by them, the way of which highlights the psychological and social characteristics of language. According to Sapirs grammatical theory, there are two types of concepts and of linguistic elements: radical elements expressing radical concepts and derivational elements expressing descriptive or derivational concepts. At the sentence level, there are relational elements used to express relational concepts which define the relationship among radical elements and construct the forms of proposition. Meanwhile, derivational elements define the meanings of radical elements, but they do not influence the meaning of a proposition. In the further analysis, Sapir revises his first classification by attributing radical elements and derivational elements to material content, with each corresponding to basic concepts and derivational concepts. Besides, he subdivides relational elements into concrete relational concepts modifying radical elements and pure relational concepts defining the sentence forms. Based on his analysis, Sapir categorizes various speeches in the world. He points out the basic concepts and pure relational concepts are essential to all languages, while derivational concepts and concrete relational concepts are common but not essential.  Sapirs psychological tendency in his grammatical research is affected by his teacher, Franz Boas, who claims that anthropology and psychology are indivisible. It is also influenced by Italian famous idealist philosopher Benedetto Croce. Besides, the linguistic worldview of the Germany philosopher and linguist William von Humboldt wields influence on Sapirs grammatical research as well. In spite of the fact that there is a lack of meticulous elaboration, a clear definition of the division standard for different grammar concepts, a thorough terminology, and a strong basis for some of his arguments, his wisdom manifested in his work can not be denied. And his contribution to the development of American structural linguistics, cognitive linguistics and psycholinguistics in the late 20th century cannot be neglected. However, Sapirs grammatical theory has received far less attention; therefore, through this discussion, the author hopes to reevaluate Sapirs contribution to theoretical linguistics, especially to the grammatical theory.