The invention relates to a united under pressure gas drainage hole sealing method and applied double-layer expansion rubber pipes thereof. The united under pressure gas drainage hole sealing method comprises (1) arranging the double-layer expansion rubber pipes which are formed by an outer-layer rubber pipe, an inner layer rubber pipe and an end socket fixing pad and enabling a water injection hole which is communicated with the outer rubber pipe and the inner rubber pipe to be axially formed in the end socket fixing pad; (2) fixing the double-layer rubber pipe at the front end of a drainage pipe; (3) enabling the water injection hole to be connected with a water injection pump through a water injection pipe and feeding the drainage pipe and the double-layer expansion rubber pipes to be in a drainage drilling hole; (4) enabling a grouting pipe which is connected with a grouting pump to be fed into the drainage drilling hole which is formed behind the double-layer expansion rubber pipe, wrapping the drainage pipe, the water injection pipe and the grouting pipe through gauze which is coated with polyurethane to form into a polyurethane hole sealing section and rapidly feeding the polyurethane hole sealing section to be in the drainage drilling hole; (5) injecting pressure water into annular space of the double-layer expansion rubber pipe through the water injection pump when the polyurethane hole sealing section achieves foaming; (6) injecting expanding cement into the drainage drilling hole which is formed between the double-layer rubber pipe and the polyurethane hole sealing section through the grouting pump; (7) enabling the drainage pipe to be connected with the drainage pump to perform gas drainage when the expanding cement is condensed.