Lee carried out statistics for sea state of Atlantic and North Pacific in 1985, offers values of significant height, spectral peak period and wind speed and possibility for each sea state, find more details in reference [16]. Since ITTC double-parameter spectrum is 1-D, but real sea wave is 3-D, energy is distributed within a broad range of frequencies and directions, in order to characterize the wave is a direction-dependent, ITTC recommend a direction spectral function