Abstract: The process and materials of double-wire deep fusion welding for marine medium and thick plate flat butt were studied and analyzed. The research showed that the double-wire submerged arc welding was used for marine medium and thick plate flat butt in order to meet the requirements of penetration and have a good inspection pass rate. By analyzing the physical and chemical properties of the welded joint, the physical and chemical properties of the welded joint meet the mechanical properties requirements of AH36 marine plate. At the same time, the microstructure of the welded joint is analyzed to observe the influence of trace elements on the microstructure of the welded joint.