with the development of hydro-elasticity, in coastal and offshore engineering, it has become very urgent to study the mechanism of wave impact process with elastic support, and to master the dynamic response change characteristics of buildings and structures under wave impact and the influence law of dynamic response on impact loads.The experimental research is based on the background of the open-type marine platform suffering from wave impact.The process of wave impact on horizontal plates under different stiffness elastic support is investigated through model tests.According to the characteristics of the impact pressure change, the impact process is divided into four different stages:impact stage, submergence stage, dehydration stage and detachment stage.In a wave period, the characteristics of the impact pressure changes at the bottom of the horizontal plate during a wave cycle are discussed and summarized.The impact duration time is defined and the distribution characteristics of the larger pressure amplitude along the bottom of the plate are summarized.To study the influence of the support stiffness and hydro-elasticity on the wave impact pressure amplitude and the dynamic response of the structure, three groups of horizontal plate with different stiffness elastic support are designed.The influence law of the support stiffness change on the distribution of the larger impact pressure amplitude along the plate bottom and the impact duration time is obtained.In the time-domain and frequency-domain, the change rule between the relative support stiffness and the relative acceleration, as well as the influence of elastic support stiffness on the frequency spectrum distribution of vibration acceleration, are discussed separately.