The abacus is a great invention in ancient China. In the old times, people used small rods to count, With the social development, numbers needed to calculate were increasingly greater, which made it impossible for the rods to fulfill the task. Thus, people invented a more advanced calculating device the abacus. Since it was convenient to use and easy to learn，the abacus was widely used in China. On the basis of the abacus, there came the mental abacus with the image of an abacus in mind to calculate the figures.