The utility model discloses a positioning seat of a gun sight or a carrying handle of a gun, which is griped on a sliding rail of a gun bore barrel and mainly comprises a body and a locking assembly. A first groove is arranged at the bottom part of the body. A second groove is arranged on the first groove. More than one jointing hole is arranged on the top surface of the body. More than one locking hole which penetrates to the first groove and is coaxially arranged is respectively arranged on the surfaces of the two sides of the body. The locking assembly mainly comprises a locking element, a nut, a spacer and a packing element. By arranging the locking element in the locking holes of the body in a penetrating way and sequentially sheathing and locking the nut, the spacer and the packing element at the end of the locking element, the body is tightly locked on the sliding rail of the gun bore barrel and is not apt to get loose.