The invention provides a gas extraction drilling hole sealing device and method. The hole sealing device comprises a cloth bag (3), a front chuck (2), a rear chuck (4) and an extraction pipe (6). The cloth bag (3) is made from an elastic thin-wall cellular material. The two ends of the cloth bag (3) are separately fixed to the front chuck (2) and the rear chuck (4). The two ends of the extraction pipe (6) separately penetrate through the front chuck (2) and the rear chuck (4). The front chuck (2) is fixedly connected with the extraction pipe (6), and the rear chuck (4) is slidably connected with the extraction pipe (6) and provided with an axial grouting pipe spigot (12). The hole sealing device is rapidly connected with a gas extraction pipe in a construction site, a hole sealing material is injected into the cloth bag (3) and later expands and seeps out of the cloth bag (3) to fill cracks around a drilling hole, sealing supporting is formed for the drilling hole, and gas leakage of the cracks around the drilling hole is also prevented. The gas extraction drilling hole sealing device and method are easy to operate, economical, environmentally friendly and good in safety.