Abstract: The paper introduced working principle,design of hardware and software and method of(installation) and use of a compartment location monitoring device in automatic loading process.The(compartment) location monitoring device took S7-300 PLC as main controller and took opposite-type(photoelectric) sensor to detect traveling position of compartment,which realized functions of real-time(location) and control of compartment position in loading coal process.The running result showed the device had good effect.