GB/T 18618-2009 focuses on the graphic parameters for the surface structure contour method in the product geometric technical specification. It clearly defines a series of graphic parameters used to describe the surface contour, such as the support length ratio of the contour figure, the average width of the contour figure, etc., and clarifies the calculation method and application scenarios. These parameters can more intuitively and comprehensively present the microscopic characteristics of the product surface. The standard provides a quantitative basis for various industries to evaluate the surface structure of products through the surface contour method, which helps to accurately control the surface mass of products and meet the high-precision requirements of different manufacturing fields.