It has been reported that large waves are formed into a group. In this paper, the effect of the spectral peakedness on the wave grouping characteristics is studied by numerical and laboratory simulation, and by statistical analysis of real sea waves. The main conclusions of this paper are as follows:
(1) The wave grouping characteristics is strongly related to the spectral peakedness. This relation is little influenced by the type of frequency spectrum, the variations of wave heights or periods during a storm and the breaking of waves in shallow water.
(2) During high seas caused by a typhoon or strong low pressure system cause wave growth, the correlation between consecutive wave heights is stronger than that of calm seas. But in a shallow region after wave breaking, the spectral peakledness or the wave grouping characteristics are weaker than that of calm seas.
(3) In order to reproduce the wave grouping characteristics in the laboratory, the spectral peakedness of waves in the laboratory should be similar to that of real sea waves. But it is difficult to reproduce the surf beats in the laboratory because of the influence of the seiche and the wave superposition by multi-reflection of waves in the channel.