Abstract: For the shortage that coal piling sensor based on limit switch cannot monitor fault signal of coal piling in time and accurately because the limit switch is easy to be influenced by external environment such as dust intrusion and humidity leading rust and corrosion, the paper proposed a design scheme of a novel mine-used I.S. sensor of coal piling based on mercury switch. The sensor uses mercury switch to send fault signal to protection and control system of belt conveyor once coal is piled up, so as to prevent continuous coal piling and protect belt conveyor. The practical application showed that the sensor is stable in running and has high reliability.