The invention discloses a plugging agent for a low-pressure leakage gas well, and a preparation method and an application method thereof. The plugging agent is prepared through the following steps: 1)stirring 0.3-0.7wt% of guanidine gum dry powder and clear water for mixing to form a mixture, and stirring at a constant temperature for 45-60 min; 2) adding 2-5% of calcium carbonate powder of whichthe particle size is 1000-2000 meshes into formed guanidine gum liquid after mixing, and stirring at the constant temperature for 20-30 min; 3) adding 1-3% of a polyvinyl alcohol fiber of which the length is 6-10 mm and the diameter is 20 Am into mixed liquid, and stirring at the constant temperature for 20-30 min; 4) adding 0.3-0.5% of an expanded particle of which the particle size is 1-3 mm into the mixed liquid, and stirring at the constant temperature for 1-3 min; 5) adding 0.3-0.5% of an expanded particle of which the particle size is 0.025-0.425 mm into the mixed liquid, and stirring at the constant temperature for 1-3 min to obtain the plugging agent for the low-pressure leakage gas well. The plugging agent can be directly used for the well repairing and leaking stoppage construction of the leakage gas well, and technical support is provided for a well repairing field well control operation; in addition, the plugging agent is simple in plug removal measure, and plug removal can be carried out through the injection of a plugging remover.