Abstract: A ship always encounters waves and may move with six degrees of freedom in the naval architecture and ocean engineering. The ship can be regarded as a rigid body simply when the motion amplitude is small. However, when the wave gets severe, the ship's motion amplitude get large and the ship hull may deforms a lot. In this situation, ship's elasticity may effects the pressure on the hull and the ship response motion, which cannot be ignored. Therefore, it is of great significance to simulate the motion of an elastic ship in waves and to study the influence of the hull elasticity, which can improve the ship performance and the navigation safety. Moving particle semi-implicit (MPS) method is a mesh free particle method based on Lagrangian representation. This method has its unique advantages in simulating problems with large deformation characteristics of free surfaces. As a traditional structural solution method, finite element method (FEM) has been widely used and has been proved with good stability, accuracy and robustness. In this paper, the advantages of MPS method and FEM method are combined and the in-house fluid-structure interaction solver MPSFEM-SJTU is used to simulate the motions of rigid and elastic hulls in regular waves. The impact of hull elasticity on the hull motion response and the pressure on the hull is analyzed. Firstly, the effect of regular wave length on the motion response of hull is studied by simulating the motion of a rigid hull in regular waves with different wavelengths. Then the motions of rigid and elastic hull in regular waves are simulated respectively. The results show that the motion amplitude of rigid hull, both pitch and heave, are greater than those of the elastic hull. and the pressure near the midship of elastic hull is greater than that of rigid hull. For the pressure distribution on elastic and hull surface, the pressure at the bottom near the midship is greater than that on the rigid hull due to the bending of the elastic ship.