In the fourth year of Tang Gaozu Li Yuan Wude (AD 62 1), he abandoned five baht and cast "Kaiyuan Bao Tong" money. Bao Tong's monetary system has been used for nearly 1300 years, which is another great achievement in China's ancient monetary history since Qin and Han Dynasties. There are mainly several aspects: "1. The first money, binary. 2. Created the era of stereotyped writing, regular script and cursive script in Qian Wen, and changed the previous forms of big seal script and small seal script. Money is no longer named by weight, but by "Bao", "Bao Tong" and "Yuanbao". Qian Wen, a great calligrapher of Kaiyuan, wrote books for poetry, reading "Kaiyuan" directly or "Kai Yuan Bao" in a spin. Qian Wen's calligraphy is a famous eight-point book, with a diameter of eight cents and a weight of two baht and four thunder (the upper structure is composed of three pins and the lower part is composed of characters), each piece weighs one or two, and each piece weighs one dollar. In the early years of Kaiyuan, Bao Tong had a profound outline and delicate writing style. The word "yuan" is picked on the left in the second horizontal direction, and then cast, with the moon pattern on the back; In the middle stage, the word "Yuan" is left-handed, right-handed or double-handed, while the word "Bao" is small, and there are often moon patterns, star patterns or star-moon patterns on the back; In the later period, the profile is wider, the foundry workers are poor and the sizes are often different.