Studying the influence mechanism of textbooks on teachers is of great significance to the compilation and improvement of textbooks. Based on the questionnaire survey on the impact of NCM (New Century Mathematics) mathematics textbooks on teachers this study selected 16 teachers for semi-structured interviews to explore how textbooks influence teachers and the factors facilitate teachers’ use of textbooks. Through the analysis of the text, it is found that the textbooks all contribute to teaching but in different ways. Besides the teachers’ internal motivation, teaching experience and teaching and research activities affect teachers’ use of textbooks.