Writing depends on the generation of writing brush. The research shows that the writing brush was produced in the Neolithic Age in China, and people in China have used it for thousands of years. Paintings and patterns on painted pottery should be painted on the embryo with brush strokes. Oracle Bone Inscriptions should also write with a brush first, and then carve with sharp tools. However, the earliest kind of writing brush was found in the Chu tomb in the middle of the Warring States period about 2,500 years ago. The earliest tombs where brushes were found were the Chu Tomb of Changtaiguan 1 in Xinyang, Henan Province and the Chu Tomb of Zuojiagongshan in Changsha, Hunan Province. Its unearthed brush is similar to the common brush now, but the pen holder is slender and the nib is 2.5 cm, which is slightly longer than the nib of modern low-profile brush. Its manufacturing method is to wrap bristles around one end of the pen holder and tie them tightly with silk thread. Changsha pen is made of fine rabbit arrow hair, which is equivalent to purple hair of later generations. It is sharp and elastic, just as Bai Juyi, a poet in the Tang Dynasty, described it as: "The purple hair nib is like a cone and sharp as a knife." It is precisely because of this kind of brush that we can see that the fonts and strokes on Chu bamboo slips are vigorous and sharp. Changtaiguan 1 Chu Tomb Brush is put in a pencil case with a small copper saw, chisel and knife in the middle. It is conceivable that these bronzes are tools used to finely process bamboo slips and carve triangular notches at braided ropes. A writing brush was also unearthed in the Qin tomb of the Warring States Period in Yunmeng Shuihudi, Hubei Province, but it was different from the above-mentioned writing brush, and it was inserted in the rod cavity, similar to today's writing method. At the same time, the tomb is also equipped with writing tools such as ink and inkstone, which are called "Four Treasures of the Study" in the Warring States period with pens and bamboo slips. Compared with modern Four Treasures of the Study, only paper and paper reflect the differences between ancient and modern times, and the other three are exactly the same. Bamboo slips, Mongolian calligraphy and silk calligraphy are all written with brush, so the strokes are elastic, sharp in starting and ending points and slightly thicker in the middle and front, which fully shows the characteristics of brush. They are different from the dignified form of inscriptions on bronze, and their strokes and styles are simpler than inscriptions on bronze. Therefore, the appearance of writing brush is not only a technological revolution, but also an artistic revolution.