Abstract: To dealing with the problems of high concealment and difficult detection of small structures of coal seam in front of the heading face in coal mine, we firstly build the a two-dimensional geoelectric model which corresponds to radar detection profiles according to the spatial distribution pattern of small geological structures (small faults and scouring fractured zones) in front of tunnel. Secondly, by making the forward modeling and migration processing to the geoelectric model based on FDTD theory, and the time domain response characteristics of the radar wave at a certain frequency to the small structure are analyzed. Finally, the explosion-proof GPR system with 50 MHz antenna are used to carry out advanced test detection for six times on the heading face of 3215 auxiliary air intake tunnel and 3218 return air tunnel in Xinjing Mine, and the numerical simulation results are used as a reference to guide the interpretation of the measured data. The results show that the response characteristics of measured radar signals of internal small structures in coal seam are similar to those of forward simulation. The 50 MHz explosion-proof antenna can effectively identify small structures within 50 meters in front of tunneling.