Abstract: According to a safety hidden danger occurred when operation personnel no intention closed to the roadheader as a roadheader was in operation, even a personal safety accident occurred, a study on a danger area warning system of the roadheader was conducted. Based on an electromagnetic field theory as a base, a I ow frequency electromagnetic wave was applied to the medium of a distance measuring and a detection of electromagnetic wave strength and the three side positioning algorithm were applied to determine a location of the operation personnel in the underground mine and to judge the personnel in or not in the danger area. The STM32F 103 embedded ARM was selected as a contral chip. The system was composited with a centralized data processing device on the roadheader and the portable mobile monitoring and measuring device with the operation person. With a simulation experiment measurement of the prototype, in a personnel positioning judgement within 0. 5~ 4.0 m, an average error was 4. 3% and a danger area positioning and warning could be realized.