The invention belongs to the technical field of a sealing-up and plugging materials, and particularly relates to a method for preparing plugging agents. The method includes smashing diatomaceous earth, bentonite, sepiolite and the like and mixing and stirring the diatomaceous earth, the bentonite, the sepiolite and water to obtain suspension; collecting emulsion from rubber trees, mixing and heating the emulsion, heavy calcium carbonate, carboxymethyl celluloses and polyamide fibers to obtain first mixtures; adding silane coupling agents into the first mixtures and carrying out ultrasonic treatment to obtain modified natural emulsion; mixing, heating and stirring the modified natural emulsion and lauroyl diethanolamine solution to obtain second mixtures, adding initiators, the suspension and cross-linking agents into the second mixtures, stirring the second mixtures, the initiators, the suspension and the cross-linking agents to obtain third mixtures and adding acrylamide solution into the third mixtures; carrying out reaction and then discharging and drying reaction products to obtain the plugging agents. The method has the advantages that the plugging agents prepared by the aid of the method are high in blocking speed and plugging success rate, formed plugging layers are high in loading capacity, good plug forming effects can be realized, repeated leakage can be prevented, and the plugging agents are little in environmental influence and free of pollution, are non-toxic and can be constructed safely and quickly.