The invention discloses a reflective trough wave advance detection method for coal roadway excavation along floor or roof of thick coal seam According to the detection method, explosives in a coal seam hole at the position on the head-on tunnel surface of the excavated coal roadway with a distance of 1/4 coal thickness from the floor or roof of the coal seam is taken as a shot point for trough wave epicentre excitation, two columns of linearly-arranged detectors are arranged in the coal seam hole at the position on two side coal walls of the excavated coal roadway with a distance of 1/4 coal thickness from the floor or roof of the coal seam, and explosion of the explosives is artificially stimulated to generate Rayleigh trough waves propagating into head-on surrounding coal seams of the excavated coal roadway; the reflective Rayleigh trough waves are received by the two detector columns on both sides of the coal roadway, energy and waveform correlation coefficient calculation of the reflective Rayleigh trough waves is carried out, the location of the geological structure interface in the surrounding coal seams of the excavated coal roadway is determined through comparison, so the purpose of the geological structure in the head-on front of the coal roadway and the coal seams at the two sides during excavation along the roof or the floor of the thick coal seam is realized.