Taking the hot rolled steel coil used for solar photovoltaic support as the control object, a robot automatic marking system was designed, which could spray mark on any position in the form of curve or straight line on the plane or arc surface, and did not need to move the steel coil. The design requirements, mechanical and electrical control system, expert intelligent alarm algorithm and software design for hot rolled coil automatic marking system were described in detail. In view of coil irregularity, robot fault, coil position deviation and other fault information, expert intelligent discrimination algorithm was used to intelligently diagnose and alarm to ensure safe production. According to the field application situation, the ABB six axis industrial robot IRB6640 was selected as the hardware core component.The results show that the system can replace manual printing, improve production efficiency, and has higher practical application value.