A large number of experiments have been done for analyzing the two important indicators -compressive strength and flexural strength, which affect computer numerical control （CNC） engraving material physical properties. Using Matlab for simulation experiment, the processing quality of different intensity brick materials is analyzed by the theory of fracture toughness. The result show that porosity is an important factor for engraving, and the research also provide a reference for further study which can improve the quality of brick carving.