Euler proved a theorem in number theory, which is now called China residue theorem, also called Sun Tzu theorem. There is a simple special case in Sunzi Suanjing, and then the general form is given by Qin, a mathematician in the Southern Song Dynasty. Later, Euler and Gauss rediscovered and proved this theorem respectively.

Euler's works were first introduced to China, dating back to about 250 years ago. They were brought to China by Russian missionaries and given to the Jesuits, a branch of Catholicism. They are collected in the library of Beijing Catholic North Church. However, in the Ming and Qing Dynasties, China's mathematics gradually declined, far behind Europe. Euler's works, which were introduced to China during the Qianlong period, can only be shelved and nobody cares. /kloc-In the mid-9th century, Euler and his works were introduced in Li's "Daiwei Pin" and China's "Trace to the Source", which were translated by American missionary John Flair. People in China began to know this great mathematician, and Euler also boarded a biography written by people in the late Qing Dynasty. At the end of the Qing Dynasty and the beginning of the Republic of China, advanced western mathematics was introduced to China, and calculus and other courses were offered in universities, which made more and more people in China know Euler and learn his mathematics.

Euler was also the mentor of all mathematicians in China and China. First of all, because everyone who enters the school for education must learn the mathematical knowledge he has created; This is because his bitter and brilliant life has given infinite inspiration to future generations and taught people how to be a man, how to learn and how to survive. Unfortunately, The Complete Works of Euler has not been introduced to any library in China.