The application of advanced welding technologies is important for improving the efficiency of hull construction processes and reducing production costs. Laser-arc hybrid welding technology, which combines the advantages of laser and normal arc welding, is of high quality and is expected to improve productivity. The Japan Ship Technology Research Association has organized the joint industry project in collaboration with a university, a classification society and some shipyards to apply this technology in the construction of general merchant ships, in which the plate thickness of the main structural member is thicker than passenger ships and high speed craft. The overview of the first phase JIP results were introduced in PRADS 2016. In this presentation, an overview of main research results of the second and third phase JIP, which are listed below, are introduced.