Abstract: In order to solve problems of poor reliability and lacking of visual and effective early-warning signal of traditional fault protection system of belt conveyor in coal mine, the paper proposed a design scheme of underground early-warning system of belt conveyor. The system adopts technologies of explosion-proof and intrinsic safety PLC and industrial field bus and realizes functions of linkage control of multi belt conveyors, fault monitoring and early-warning in forms of words and sound. The application result showed that the system is stable in running and strong in reliability, which improves efficiency of fault early-warning and treatment of belt conveyor.