Consciously infiltration of function thought in teaching can spread students 'thinking, effectively help students to reduce the difficulty of the problem when solving problems, improve the efficiency of problem solving and cultivate students' good thinking quality and modeling ability. This paper starts from the concept of function, introduces the idea of function thought and shows the specific application of function thought in equation, inequality, sequence and geometry, and discusses the wide application of function thought in high school mathematics problem solving to shows the importance of infiltrating function thought in elementary mathematics teaching.