The commonly used wharf top elevation calculation methods and the two-dimensional extreme value distribution in international engineering are introduced，and that the main variables considered in the wharf top elevation calculation are wave height and water level is pointed out. Taking the Guinea bauxite export project as an example，the definition of the wave crest height’s return period is proposed. The extreme value distribution theory is adopted to fit the water level and wave height respectively，and the appropriate joint extreme value distribution model of water level and wave height is selected. From the comparative analysis of the calculation results of the case，it can be found that the concept of the return period of the wave crest surface height is introduced，and the wharf top elevation calculated by the joint extreme value distribution of water level and wave height is lower than the wharf top elevation calculated by the two separate one-dimensional extreme value distributions. In the area where wave force is non-dominant，the conclusion benefits the EPC contractor by reducing the project cost and improving its performance ability.