Abstract: Topic diagram is a significant part of primary mathematics textbooks, which bears a great deal of functions, such as introducing new knowledge of mathematics, displaying the main line of teaching, directing students to learn, keeping in touch with real life, comprehending mathematics thoughts, and infiltrating the ideological and moral education, etc. Many top- ic diagrams in primary mathematics textbooks carry two or more functions, not merely one single function. If teachers could understand the functions of these topic diagrams clearly, it will enhance their abilities of the secondary exploration of the text- books and promote students to master the“four basics” and the“four abilities” as well and help implement the development of their core qualities.