Although sketch painting has various styles and different techniques, it can be roughly divided into three basic forms: line modeling method, light and dark tone modeling method and line-surface combination modeling method. Line Modeling The traditional painting form in China is line modeling. In the long-term artistic practice, China painters of past dynasties have accumulated rich experience in line drawing and left countless artistic treasures. Although western painting is dominated by light and shade modeling, the application of lines has never stopped, and many painting masters are also masters of line modeling. Line modeling pays attention to the change and unity of lines. Rigid and soft, priorities, cadence, straight and dense, all reflect beautiful form and vivid charm. The line modeling method in basic sketch training, as long as you learn to use concise and clear lines to summarize the physical structure characteristics of objects and cultivate the ability to observe and analyze the relationship between physical structures, can show a certain three-dimensional and spatial effect. Light and dark tone modeling uses the basic laws of light and dark tone to express the shape, texture, three-dimensional and spatial effects of objects under the irradiation of light, which is the essence of western painting, and it can truly express the natural state of five spices. Sculpting statues with light and dark blocks is the basic form factor of this modeling method. The treatment of light and dark levels of the picture and the expression of three-dimensional space are based on the analysis and understanding of the body surface and the vivid grasp of the law of light and dark. Light and dark tone modeling is one of the main methods for us to learn sketch. The modeling method of combining lines with surfaces and combining light and shade not only has a sense of rhythm of lines, but also keeps the three-dimensional sense of lost images, which is a kind of modelling technique commonly used in sketch. The combination of line and surface in basic sketch training is not a simple combination of lines in light and dark sketch, but an organic combination of line and surface, but a modeling method that pays attention to light and dark shadow and contrast between light and dark, and highlights the structural relationship. Its learning mainly lies in analyzing and studying anatomical structure and understanding and mastering structural factors in modeling.