Abstract: Coal mine monitoring system based on dual positioning can monitor gas concentration and personnel location information of underground. When the gas concentration is too high, the system will send alarm information to guarantee the safety of personnel. The system locates underground personnel by using three edge positioning algorithm and the MAP algorithm, so that the system keep the accuracy of the personnel positioning when the system in normal state and mine gas exlosion, collapse and other emergency states. At the same time, the system supports short-message alarm function.