The invention relates to a twin-hull semi-submersible barge for drying towing transportation of a semisubmersible drilling platform and an operating method. The twin-hull semi-submersible barge comprises a barge hull, wherein the barge hull consists of two monomer semi-submersible barges; cofferdams adopting a double-layer structure are separately arranged in the positions close to a bow and a stern, in the monomer semi-submersible barge hulls; annular girder slideways are separately arranged on two sides of each cofferdam; a hydraulic mechanism is arranged in an upper layer structure of each cofferdam; a base of each hydraulic mechanism is fixed to the hull; the two monomer semi-submersible barges are connected by two annular rigid girders to form the barge hull; two ends of one of the annular rigid girders are separately in sliding connection to the corresponding cofferdams close to the bow, of the two monomer semi-submersible barges through the corresponding annular girder slideways; the end part of the corresponding annular rigid girder penetrates through cofferdam walls of the corresponding cofferdams; another annular rigid girder is in sliding connection to the corresponding cofferdams close to the stern, of the two monomer semi-submersible barges through the corresponding annular girder slideways; and after penetrating through the cofferdam walls of the corresponding cofferdams, a hydraulic rod extending end of each hydraulic mechanism is connected with the end parts of the corresponding annular rigid girders.