The invention relates to the field of well workover plugging construction in gas fields, and in particular relates to a preparation device for a gas well workover and killing plugging agent and a usemethod of the device. According to the whole device provided by the invention, a direct injection mixing funnel for fluid preparation and stirrers are arranged, a fluid can be independently prepared without cooperation of a pump truck, so that the cooperation operation time of the well killing pump truck is saved, and the construction costs of the well killing pump truck are reduced; multiple skid-mounted tanks are used in the whole device, especially three skid-mounted tanks are used, each skid-mounted tank is equipped with one stirrer, each skid-mounted tank adopts an independent water supply pipeline and water outlet pipeline, each skid-mounted tank can realize preparation and storage of different plugging well killing fluids, the three skid-mounted tanks in the whole device are separately equipped with one connection opening of a water pipe of the well killing pump truck, the plugging gas well workover and killing fluid can be injected into the well in a single or different combination manners by the well killing pump truck, the whole device adopts three skid-mounted tanks, and the manner is most reasonable and convenient for transportation; and the device is convenient to transport.