Liu Hui (born around 250 AD) was a great mathematician in ancient China. His representative works "Nine Arithmetic Notes" and "Arithmetic Classics on the Island" are the most precious mathematical heritages in China. Liu Hui was the first person in the world to put forward the concept of decimal. He correctly put forward the concept of positive and negative numbers and the rules of addition and subtraction. In this paper, the "cyclotomic method" is put forward, and the pi is calculated to be 3. 14. Liu Hui's theory of "carefully cutting the garden, the loss is not great, the hard cutting can't be achieved, and nothing is lost when it is in tune with the garden" is considered as the representative work of China's ancient limit concept.