Nowadays，the number of over-panamax size container and large size coal cargo vessels are increasing. For handling such large vessels,deep water quays are under construction in many ports. Therefore, it is becoming very important to compute the required extension length of breakwater to ensure enough trauquility for berths.
　For the computation,the wave transformation model is employed to estimate the wave condition at the entrance of harbor. Meanwhile,harbor tranquility estimation model is applied for the wave height inside harbor.
　Generally it takes a long time and a lot of labor to carry out the both model in the present system.
　We have developed a new computation system to estimate the wave transformation and wave heights in harbor continuonsly applying the water depth data base.
　The new system is called Wave Transformation System. The system is able to be carried out in a super computer,a EWS, and a personal computer, though the former computation was done only in a multi-purpose computer. The modification of topography data, execution of computaion monitoring of calculation and print-out of results are able to be operated in the personal computer.
　A new system is expected to be employed to estimate harbor tranquility for a new deep quay and to calculate design waves for breakwaters.