High-rise pile cap foundation of offshore wind turbine is used in Donghai Bridge windfarm, East China Sea. The wave load characteristic of this new type of fixed structure has been paid close attention in engineering. In this investigation, based on Navier-Stokes equation, a fully nonlinear numerical wave tank was established for this high-rise pile cap foundation, and the wave loads and moments were obtained by integrating pressure over the surface of the structures. The effects of interaction between the cap and the piles are discussed in detail. In case of extreme wave height, the results indicate that the wave load on the piles with the cap increases by about 30 percent of those without it, and the maximum wave load is nearly doubled. The horizontal wave load on the cap with the piles increases by about 15 percent, while the vertical wave load decreases slightly. In addition, simply using Morison equation will seriously underestimate the wave loads of the piles.