Currently, some manual segmentation problems exist in multi-beam waterjet cutting process drawings, such as low efficiency, incomplete segmentation and so on. In order to solve the problems, this paper designs a set of criteria for multi-beam cutting process and proposes the method of partition-classification trim, then uses the secondary development tool which is embedded in AutoCAD to program three user-defined commands, and these commands can partition the drawing by region, classify and trim the entities in the cutting process drawing. Through inputting the three simple commands on the command lines, it can realize automatic segmentation of cutting process drawings. Finally, the feasibility of this method is proved by a segmentation experiment. It can effectively solve the problems which exist in manual segmentation and greatly improve work efficiency.