In some ports facing to open sea, moored ships sometimes move so hard that cargo handling or mooring becomes difficult, and the mooring lines or fenders have broken in serious case. Then we focus on the wave and wind conditions of inside and outside of a port facing to Sea of Japan where moored ships move hard in winter and find the existence of the "long period wave". One year wave data of inside and outside of other port facing to East China Sea are observed and the spectrum analysis of them is done, and we ensure the existence of long period wave exist and its energy increases inside of the port. Firstly, we simulate the phenomenon of moored 60, 000 DWT bulk ship motions using wave data included "long period wave". Secondly, we change mooring methods and simulate the ship motion at the same condition, and then compare the ship motions, mooring line tensions and fender reaction forces. As the result, we consider the effect of the better mooring methods in ports facing to open sea in case of stormy weather.