The utility model discloses a high-sensitive ultrahigh frequency sensor. Two ends of a metal housing of the high-sensitive ultrahigh frequency sensor are respectively connected with a metal cover plate and an epoxy resin plate to form an enclosed cavity, and the cavity is divided into two enclosed spaces by a shielding plate; an inner wall of the metal housing of the lower space is provided with a fixed frame, an amplifying plate is installed on the fixed frame, and an internal surface of the epoxy resin plate is equipped with an antenna plate; a body wall of the metal housing of the upper space is provided with an aviation plug and an N-type head, and the antenna plate, the amplifying plate, the aviation plug and the N-type head are successively in series with each other through leads; and a lower end of the metal housing is fixedly connected with a circular plate. With the high-sensitive ultrahigh frequency sensor, extraneous electromagnetic signals can be well shielded, electromagnetic waves generated by partial discharge inside high-voltage paralleling reactors can be received more accurately by the amplifying plate and the antenna plate in the housing, and installation is convenient; and the high-sensitive ultrahigh frequency sensor is high in anti-interference capability, wide in signal bandwidth, large in dynamic range and high in sensitivity.