A water-exchanging slit caisson can exchange water inside of the harbors to reducee nvironmental pollution. In order to clarify the hydraulic characteristics of the water-exchanging slit caisson, three-dimensionanl numerical simulation was carried out, and quantities of exchanging water through the hole and wave transmitting coefficient were calculated. And the results were verified by using model experiments. It is confirmed that the quantities of exchanging water were related to the period of wave. So the numerical simulation is useful to predict the hydraulic characteristics of the caisson.
