A submerged arc additive manufacturing method for a metal structure having great mechanical properties. The submerged arc welding method for forming the metal structure is such that: two electrodes of a welding power source (12) respectively are connected to a welding torch (6, 401, 602, and 603) and to a substrate (2, 201, 202, and 203), a granular flux (3, 301, 302, and 303) and a metal welding wire (1, 101, 102, and 103) are simultaneously conveyed onto a surface of the substrate, power is turned on, an electric arc is produced between the substrate and the welding wire covered by the flux, thus allowing the welding wire and the surface of the substrate to be partly molten to form a weld pool on the surface of the substrate, conveyance of the welding wire and the flux is continued, and relative movement paths of the welding torch and of the substrate are controlled on the basis of modulus data of parts, thus implementing layer-by-layer hardfacing deposition on the substrate to form the metal structure.