The utility model discloses a device for tightening a wire clamp, and the device comprises a ratchet wheel sleeve, a cross-core square nail, a wrench socket, and a reverse ratchet suite, wherein the bottom end of the ratchet wheel sleeve is fixedly equipped with a ratchet-wheel sleeve wrench. One end of the cross-core square nail is inserted in the ratchet wheel sleeve in a direction perpendicular to the ratchet-wheel sleeve wrench. The other end of the cross-core square nail is connected with the wrench socket through a pin. The reverse ratchet suite is disposed at the central part of the cross-core square nail in a cup-joint manner. The reverse ratchet suite is provided with a handle in the direction perpendicular to the cross-core square nail. According to the utility model, when the ratchet wheel sleeve sleeves a loosened parallel-groove-clamp screw, a drainage wire is held through the reverse ratchet suite, and the ratchet-wheel sleeve wrench rotates, thereby achieving the purpose of fastening the loosened screw. Moreover, the operation process is simple and convenient.