Abstract:Floating preload condition is a special state with shallow draft of jack-up platform and the fluctuation of the water line affects the wave force on the platform significantly, so it is not accuracy enough if applying the first-order theory only in hydrodynamic calculation under this condition. Taking a jack-up offshore oil drilling platform as the research object, the hydrodynamic analysis model of the platform is established. In the shallow draft state, considering the second-order wave force on the platform, the high-order boundary element method is used to solve the first-order and second-order hydrodynamic problems of the platform. Through numerical simulation, the numerical calculation results of wave force and motion response of the platform under various incident wave frequencies are given. The results show that the second-order wave force has a great influence on the amplitude of wave force in the horizontal direction under floating preload condition, and the it can’t be ignored in both horizontal and vertical directions from the perspective of motion response.