The ratio of the height of reflected waves to that of incident waves appears to be necessary to explain the phenomenon of wave reflection. The reflection coefficient of water waves is an important fact for every problem of wave and structure interaction. The study of reflection of slit-type structures is being continued steadily, but the structures involve many problems to be solved. Therefore, we tried the experiment on reflection and transmission of waves with slit-type structures of vertical square pile. In order to measure reflection coefficients, we used Healy's method which is based on the theory of small amplitude waves. From the experimental data, the several conclussions of reflection and transmission coefficients can be described in this paper.
