In order to solve the problem that the representation of disk workpieces is difficult in the case reasoning method, this paper proposes a method of case representation and retrieval of disk workpieces based on UML. This method uses the unified modeling language to decompose the disk workpiece case into functional attributes, material attributes, geometric attributes and processing attribute, and strengthens the logical relationship between each attribute. Disk workpieces are different from other geometric workpieces and have the characteristic of cyclotron symmetry. According to this characteristic of disk workpiece, the distribution attribute and topological relationship of disk workpiece are introduced to describe the geometric feature and spatial distribution of disk workpiece, and the geometric attribute description and similarity calculation of disk parts are realized.