The invention relates to a self-balancing type horizontal correcting device for correcting and resetting an old bridge. The self-balancing type horizontal correcting device comprises a fixed bracket, a sliding bracket, a pushing jack, a vertical jack, a sliding plate and wedge blocks, wherein the fixed bracket comprises a base plate and a baffle, wherein the base plate is arranged at the bottom end, and the baffle is arranged at any end of the base plate; the sliding bracket comprises a base plate arranged at the bottom end and a baffle arranged on the base plate; the base plate of the fixed bracket is paved under the sliding plate; the base plate of the sliding bracket is paved above the sliding plate; the front end of the pushing jack is jacked on the baffle of the sliding bracket, and the rear end of the pushing jack is jacked on the baffle of the fixed bracket; the vertical jack is arranged on the base plate of the sliding bracket; and the wedge blocks are respectively arranged at the upper end and lower end of the vertical jack. The self-balancing type horizontal correcting device has a simple structure, is reasonable in design, can fully utilize the available space of a beam bottom and the top of a pier column cover beam, requires no additional construction support basis and is reusable. The invention also provides a construction method for the horizontal correcting device for correcting and resetting the old bridge.