Expansion: After Xiao Zhuan and Qin Shihuang unified the six countries (22 BC1year), the policy of "all books are written in the same language, and all cars are on the same track" was implemented. Li Si, the prime minister, was in charge of the policy of unified measurement. On the basis of the original seal script used by Qin State, he simplified it and created a Chinese writing form of unified characters. Popular from the Qin Dynasty to the end of the Western Han Dynasty (about 8 AD), it was gradually replaced by official script.

But because of its beautiful font and long ancient rhyme, it has always been favored by calligraphers. Because of its complex strokes and simple form, it is possible to add twists and turns and seal cutting at will, especially the official seal that needs anti-counterfeiting. Seal script was always used until the collapse of feudal dynasty and the emergence of modern new anti-counterfeiting technology.

During the Spring and Autumn Period and the Warring States Period, Chinese characters in different countries were different in simplicity and complexity. After Qin Shihuang destroyed the Six Kingdoms, he ordered the Qin Dynasty's Biography as the standard to unify the national characters. Seal script, also known as "seal script", is a combination of small seal script and big seal script. Because it is customary to call "seal script" big seal script, later generations often refer to "seal script" exclusively.

Chinese characters developed into seal script stage, and gradually began to finalize the design (outline, strokes and structure), which weakened the pictographic meaning, made the characters more symbolic, and reduced the confusion and difficulties in writing and reading. This is the first time in the history of China to standardize Chinese characters on a large scale by administrative means.

The Qin Dynasty unified the national characters with the sorted seal script, which not only basically eliminated the phenomenon of different lines of characters in different places, but also greatly changed the situation of different fonts in ancient Chinese, which is of great significance in the history of China characters development.