Wave basin experiments of a blunt ship model were conducted comprehensively in regular and irregular extreme waves. Six degrees of motions, vertical as well as horizontal bending moments at the midship section, hydrodynamic pressures on the hull at 20 locations, relative wave elevations at 5 locations and green sea loads on fore deck and two hatch covers were measured in a quite systemic manner. The selected regular wave conditions were 5 different wave encountering angles, 6 different wave frequencies and 4 different incident-wave heights, while the selected irregular ones were only the head and beam seas with the significant wave height of 10.6 meters and the mean wave period of 14 seconds. The main purpose of the experiments is to investigate and understand the characteristics on the wave-induced motions, hydrodynamic pressures and loads in extreme waves especially as the green sea loading on the decks. And the final objective of this study is to establish practical approaches of evaluating wave loads in extreme waves qualitatively and quantitatively. As the first report of this study, this paper mainly introduces the results obtained by the experiments. The nonlinear characteristics with respect to wave height of wave-induced ship motions and loads in extreme waves are also discussed with the phenomenon of the green sea loading on the decks.