In hard-pen calligraphy works, seal is a common decorative element, which represents the author's recognition and authority of his own works. According to their different forms and uses, they can be divided into two categories: famous chapters and leisure chapters. Famous seals are engraved with the author's name, font size and other information, and most of them use simple and clear shapes such as small circles or squares. Leisure articles include various types, such as year number, elegant taste, vegetarian restaurant and so on. Most of them are oval or rectangular to highlight their unique attributes.