Expansion type blanking plug operating under pressure

The invention belongs to the technical field of oil gas equipment, and discloses an under-pressure operation expansion type blanking plug which comprises a positioner and a blanking plug body, the positioner is installed in an oil pipe, and a horn mouth structure with the diameter gradually reduced is arranged in the positioner; a mechanical switch, a motor and a hydraulic transmission system which are sequentially connected are arranged in the blanking plug body, and a rubber sealing piece is arranged on the blanking plug body and connected with the hydraulic transmission system. Elastic claws are uniformly distributed on the circumference of the blanking plug body, the elastic claws are telescopically mounted on the blanking plug body, and the position of the mechanical switch is opposite to that of the elastic claws. According to the expansion type blanking plug working under pressure, the positioner is installed in the oil pipe in advance, when the oil pipe needs to be replaced subsequently, the blanking