Abstract: The overall process flow and each process in automatic hot acid etching macrostructure inspection system of square billet were inveatigated. The design principles of the entire system, as well as the equipment composition and process flow of the sample receiving and processing system, acid etching and imaging system, environmental protection device and automatic control system, were expounded. The system had achieved the full-process intelligent detection of hot acid corrosion for square billet. After its commissioning, the work efficiency had increased by 40% compared with the manual mode, and the labor productivity had risen by 50%. Moreover, it had low operation and maintenance costs, and the material cost was only 1/3 of the high-speed circular saw solution. Finally, the key points of the laboratory design for the system were sorted out, and the development prospects of automatic macrostructure inspection system process were prospected.