In an attempt to develop a systematic series of wave spectra covering a variety of spectral shapes observed in the ocean, this paper presents a newly developed series of wave spectra which involves six parameters. In the development of the six-parameter wave spectra, the spectra are decomposed into two parts. Each part is expressed by a mathematical formula with three parameters, and the total spectrum is expressed by the combination of two sets of three-parameter spectra. Results of analysis have shown that the six-parameter wave spectra thus derived appear to represent almost all stages of development of a sea during a storm. Then, from the statistical analysis of 800 spectra observed at the North Atlantic Ocean, the values of the six-parameters are expressed in terms of significant wave height so that a family of spectra for a desired sea severity can be generated.