Abstract: In this paper, by using the method of establishment a transfer function, the wave forces spectra on cylinders and the characteristics values are obtained from in incident wave spectra. The JONSWAP spcetra in used as a incident frequency spectra the Directional distribution function is square cosinusoidal funcation. The wave forces coeficients is two to four cylinders with different arrangment is computated wich can by used for engineering design. A comparison of computational and experimental results of single cylinder with frequency spectra is made and the agreement is satisfactory.

Key words: random waves, wave force, frequency spectra directional spectra, transfer function