How to guide children to preview mathematics, we must first understand what preview is. The new curriculum standard points out that preview is an independent exploration activity of learning individuals. Students use their existing knowledge, life experience and learning methods to explore independently, thus stimulating students' interest in learning, enhancing their confidence in learning mathematics well and promoting their development. To put it simply, preview means that the teacher asks the students to read the textbooks in advance and learn new knowledge before starting a new class. And think independently and explore a way of learning to acquire new knowledge. Preview is students' independent study of new teaching materials before class, and it is the prelude and overture of classroom teaching.