Abstract: With the large scale development trend, the lengths of ships are constantly increasing. As a result, high strength steel is widely used due to the demand of lightweight design of ship structures. Hull girder of the ship, in particular, becomes much more flexible than those of small and medium-sized ships. This results in different characteristics of springing behaviors of ship structures when the ship travels on the sea. In this paper, a large engineering ship is taken as the research subject in order to study its low-and high-frequency wave induced load responses in waves. Two kinds of steel girders with different transverse-section moments of inertia are used to simulate original and changed stiffness in a segmented model. The 3D hydroelasticity theory is employed to predict responses of the ship in waves, and comparison analysis is also conducted between experimental and theoretical results. It is shown that springing behavior is prone to happen with low hull-girder stiffness, and continual springing behavior will result in serious fatigue damage to ship structures. The necessity of considering the hull-girder stiffness as an important parameter in the structural optimization design of large ships is thus verified as the effect of hull-girder stiffness on springing behaviors cannot be neglected.