After Qin Shihuang unified the six countries (22 BC1year), he implemented the policy of "the same language in words and the same track in cars", and the unified measurement was in the charge of Prime Minister Lisi. On the basis of the original seal script used by Qin, he simplified it and created a unified writing form of Chinese 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 complicated strokes and peculiar forms, 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 the feudal dynasty and the emergence of modern new anti-counterfeiting technologies.