Abstract: The reflection and transmission of small amplitude surface wave by two vertical po-rous plates with different penneabilities and spacing l fixed in the middle of an infinitely long channel of constant depth are studied.Analytical solutions in closed foims are obtained for the surface wave profiles.It is found that when the spacing l is a multiple of the half-wave length of the incident wave, both the reflected and transmitted wave amplitudes have the maximum values.In this case,the optimum wave-dissipation rate is less than 0.5. On the other hand,when the spacing l is a quarter-wavelength plus a multiple of the half-wavelength of the inci-dence wave, not only the reflected wave amplitude but also the transmitted wave amplitude re-duce to minima。In this case, the optimum wave-dissipation rate is greater than 0.5. Moreover,the condition related to non-reflected wave is obtained.

Key words: porous plates, surface wave, reflected and transmitted waves