This is the research result of Piaget's theory of stages of children's cognitive development. Mathematics is the gymnastics of thinking. The development of children's thinking at the age of 0-2 needs to start with motion perception, and children at the age of 2-5 need to think with objects or images. At the age of 5-7, it gradually transits to abstract logical thinking, and at the age of 7- 12, it continues to develop logical thinking, which is called mental arithmetic.