The symbol of the formation of a complete system of ancient mathematics in China is Nine Chapters Arithmetic, which is the first mathematical monograph written by ancient Han scholars in China, and also the most important of the ten computational classics. The book is very rich in content and systematically summarizes the mathematical achievements in the Warring States, Qin and Han Dynasties. At the same time, Nine Chapters Arithmetic has its unique achievements in mathematics. It not only mentioned fractions at the earliest time, but also recorded the remaining and missing problems at the earliest time. The chapter "Equation" also expounds the negative number and its addition and subtraction algorithm for the first time in the history of world mathematics. It should be noted that "Nine Chapters Arithmetic" has no author. It is a comprehensive historical work and the most advanced applied mathematics in the world at that time. Its appearance marks the formation of a complete system of ancient mathematics in China.