An apparatus includes a current excitation source, a roadheader telescopic protection cylinder, an electric rotating apparatus, auxiliary cutting teeth, a cutting head entity, a transmission shaft, an optical fiber ring protective housing, an optical fiber ring, an optical fiber current sensor control unit and a recovery electrode. The apparatus transmits an auxiliary current Ie and a monitoring current Id to a coal seam. The auxiliary current Ie and the monitoring current Id are homologous currents that are incompatible, and the auxiliary current Ie squeezes the monitoring current Id, so the monitoring current Id monitors the environment of the coal seam. The monitoring current Id flows to the coal seam as, and a return current If flows through the transmission shaft and a roadheader expansion part. The optical fiber ring measures the return current If, when the roadheader is heading forward and encounters abnormal geological bodies.