Mooring troubles due to moored ship motions are very serious problem in a harbour facing the open sea from the point of view of the port operation. Some countermeasures are proposed against moored ship motions. However, there are few harbours with mooring systems considering long period ship motions. This shows that other operational systems are necessary using database of waves or typhoons.In this study, we focus on a harbour facing the Pacific Ocean, and research on mooring troubles which are happened in 1997-1999 at first. It is cleared that most of mooring troubles happens under the condition with the influence of swells or long period waves due to typhoons. Thus, relational analyses are carried out using observed wave data by NOWPHAS system and typhoon data. Some relations can be found among mooring troubles, observed wave conditions, and typhoons as the basic information of the wave prediction.