The professional knowledge of teachers is the theoretical system and experience system that distinguishes teachers'profession from other professions. According to Shulman, president of Carnegy, a teacher's essential professional knowledge should include knowledge of the following subjects: General Pedagogical Knowledge; Curriculum Knowledge; subject pedagogical knowledge; students and their characteristics; Knowledge of educational context; Knowledge of educational objective, value, philosophy and historical origin. The subject teaching knowledge is the core of the above-mentioned seven kinds of knowledge, and it is the knowledge that teachers present and explain effectively in the face of specific problems, after "activating" subject knowledge, student knowledge, curriculum knowledge, evaluation knowledge, general teaching method knowledge, and so on, dynamic knowledge is formed by making judgment, selection and reorganization through one's own values, it is the result of teachers'active construction and creation. The process of forming the subject teaching knowledge is the process of teachers'Life Movement and the process of teachers'personality development. It can be said that teachers in the creation of new subject teaching knowledge, but also create a new themselves. Subject teaching knowledge is an important knowledge for subject teaching experts, and it is a special form for teachers to understand their specialities.