Abstract: When the width of coal face is large, influenced by the signal penetration ability, the conventional method of detecting the internal structure of working face can not effectively penetrate, so that the detection effect is not ideal. The single-pole power supply gradient electric sounding method which can realize long distance detection with flexible design of polar pitch is designed. Electrodes are equipped in both sides of the tunnel in the face and lateral wall of coal seam respectively to detect the sandstone intrusions inside the wide working face by counter directional bedding, which overcomes the difficulty of bad contact between the electrodes and the coal seam caused by side spalling and fractures. Under the conditions of summarizing the characteristics of internal dielectric change in coal mining face, the method of resistivity distribution is reconstructed by observing the potential difference to deduce the distribution range, extension, thickness change laws of sandstone intrusions in the coal seam. Lane exploration and later mining revealed that the detection results were consistent with the actual situation.