In the actual coalfield geophysical exploration, conventional surface seismic exploration technology cannot carry out fine detection of small faults, collapse columns, and rock parting in coal seams. Compared with surface seismic exploration, in- seam seismic exploration is directly excited in the coal seam, with strong energy and large range, which can accurately detect the small frame structure in the coal seam. Methods:Compared with ground seismic exploration, in- seam seismic exploration has the advantages of high efficiency, accuracy and high resolution, and its detection distance is large, anti- interference ability and obvious waveform in coal mine exploration, and in- seam seismic exploration can accurately detect abnormal structures such as discontinuities, faults, collapse columns, scouring zones and other abnormal structures in coal seam space, and other geological information inside the working face can also be obtained, which has significant advantages in detecting small structures. According to the characteristics of reflected in- seam wave seismic data, an effective fine processing technology is proposed in this paper. Through experimental research on key technologies such as dispersion analysis and envelope superposition, the imaging accuracy is improved, and then the microstructure such as small faults in coal seam is accurately identified.Results: According to the results of the reflected trough wave detection, it is speculated that there is a fault with a drop greater than 6 m on the west side of the working face transport trough, and the fault extends from the north side of the working face from northeast to southwest into the west side area, and the fault extends farther. In the actual reflection slot wave detection in this paper, it is subject to a certain degree of noise at the bottom of the well, power frequency electromagnetic and construction interference during the firing process, and a small number of abnormal seismic tracks occur, and the signal- to- noise ratio is better improved by related pretreatment and denoising technology.Conclusions:In the actual reflection in- seam wave detection in this paper, it is subject to a certain degree of noise at the bottom of the well, power frequency electromagnetic wave and construction interference during the firing process, and a small number of abnormal seismic tracks appear, and the signal- to- noise ratio is better improved by related pretreatment and denoising technology. The application research in actual coalfield shows that the reflected in- seam wave exploration accurately identifies the small fault in the coal seam, which verifies the practicality of the reflected in- seam seismic exploration technology and the effectiveness of the seismic data processing technology of the reflected in- seam wave.