Abstract: In order to improve the welding efficiency of ship structure and building structure, high heat input welding should be used. Two Japanese companies had developed many technologies, including effective control of grain size in HAZ by using TiN, refining grain by ferrite nucleation, and the control of microstructure in HAZ and the TMCP controlled rolling technology, etc. By combining these new technologies, high strength steels for welding with various high heat inputs were successfully developed, which could be used in shipbuilding, buildings, bridges and ensure the toughness of HAZ with high heat input.