One of the six methods of ancient painting books, the painting theory of Sheikh in ancient southern Qi Dynasty. "Writing with brush bone" or "writing with brush bone" refers to the so-called bone writing and its closely related brushwork. "Bone method" was originally a concept of learning from each other, and later became a language for people to observe the identity and characteristics of characters, which was very popular in the Han and Wei Dynasties. In addition to the word "charm", Wei Jin people often use comments such as "bone" and "body". The word "bone" is a figurative concept, and "bone" and "bone strength" illustrate the straightforwardness, decisiveness and external performance of people's inner character in a figurative way. The word "bone" is used in the book theory, such as "those who are good at writing are rich in bone, and those who are not good at writing are rich in meat" ("Pen Map"), which refers to strength and pen power. The appearance of "bone" in painting theory began in Gu Kaizhi, such as commenting on Zhou Benji: "Diemirun has bone method"; Comment on Han Benji: "Natural bones are more exquisite and less" and so on. The words "bone method" and "heavenly bone" here are also related to people's articles and faces, and refer to the identity temperament reflected by the bones of the painted characters. Sheikh's application of "bone method" has turned to the artistic expression of bone strength and strength beauty with pen. At that time, all paintings were sketching lines, and the structure, posture and expression of objects could only be expressed by the accuracy, strength and change of lines. Therefore, he borrowed the "bone method" to illustrate the artistry of using a pen, including the meaning of pen power, sense of force (similar to the book theory of "a good writer has many bones") and structural expression. This can be seen from the words "pen for bone stalk", "novel pen", "weak handwriting" and "beyond handwriting". After Sheikh, the bone method has become an important standard for evaluating painting in past dynasties, which is the corresponding aesthetic principle inevitably produced by the unique materials and tools of traditional painting and national style, which in turn promoted the perfect development of national style painting.