Abstract: In order to meet requirements of high efficient and reliable running of complete conveyors on fully-mechanized face of coal mine with annual production capacity of 10 million tons,a real-time system of working condition monitoring and fault diagnosis of conveyors of fully-mechanized face based on PLC was designed.The hardware constitution of the system was introduced briefly and the whole function and realization of the system's program were expounded in details.The system integrates monitoring of running state,detection of running parameters,data recording and fault diagnosis as a whole and has functions of remote and in situ monitoring and fault diagnosis for working condition of speed reducers and motors of complete conveyors on fully-mechanized face.The debugging results in field showed that the system has characteristics of stable running,accurate data display,and high reliability of fault diagnosis.