Along with the development in offshore technology, the offshore platforms are gradually becoming larger and more complex. Recent development of oil and gas field in the deepwater region often involves multiple floating platforms adjacent to each other. Wave free surface associated with the air-gap design is one of the most important issues as the interaction between the platforms can complicate the hydrodynamics further. In this paper, the nonlinearity of incident wave and scattered wave are considered in diffraction analysis based on the potential theory. In addition, the nonlinear incident wave is considered to capture the nonlinear features of free surface due to wave diffraction and radiation. The wave surface amplitude around a multi-body platforms system is numerically analyzed in the frequency domain and compared with the numerical results of a single platform. The distribution of wave surface amplitude with different scatter parameter at different wave steepness is investigated to examine the relationship between the two parameters critical to the nonlinear wave surface elevation.