In this study we set a pitching fluid tank on a floating platform with two vertical springs on both sides to support it. By assuming that the fluid in the tank is un-compressible and in-viscous and that there are no breaking waves existing, we observe the dynamic responses of the fluid in the tank and the interactions between the tank and the floating platform under wave forces. Using numerical simulations to analyze sloshing forces of the fluid and responses of the floating platform, we compute the work of the couple system in different cases and finally get normalizing results to provide for different sizes. The main purpose of this study is to gather wave power into a composite floating platform via the vibration of the floating and the pitching motion of the tank induced by wave forces, to transform the wave power into mechanical energy, and to reduce the angle of the vibration, making the floating platform stable and improving the safety.