The invention discloses a sealing method suitable for high-temperature nitrogen injection into a coal seam drilling hole. A double-layer pipe structure composed of PE pipes and iron pipes is adopted,and the iron pipes are fixed in the PE pipes by rubber fixing devices, and the connection between the PE pipes and the connection between the iron pipes are threaded connections, which facilitates installation. Since the iron pipes are not in direct contact with the PE pipes, when high-temperature nitrogen is injected into the drilling hole through a reducing iron pipe and the iron pipes, since rubber transfers heat slowly and a space between the PE pipes and the iron pipes is large, the temperature of the high-temperature nitrogen cannot be directly transmitted to the PE pipes and the borehole wall through the iron pipe, thereby ensuring the heat insulation effect on the PE pipes and the drilling hole wall through the iron pipes, so a heat insulation effect of the PE pipes and the drilling hole wall is ensured, and drilling hole air leakage caused by the PE pipe deformation caused by heat transfer is avoided. At the same time, a coal wall with severe air leakage near the drilling holeis blocked by a binding material, the sealing performance in the drilling hole is ensured to make the drilling hole have a better pressure accumulating environment, and the need for high-temperaturenitrogen transmission and cracking after nitrogen pressure accumulation is met.