Simulation method to calculate ship's motions and mooring forces of moored ship was developed. In this method irregularities of waves and wind forces and non-linear characteristics of mooring system are considered. The results of simulation method were compared with the results of hydraulic model tests. Then followings were concluded from this study:
1)　Wave forces to which the ship moored in front of vertical wall was subjected are obtained by superposing incident and reflected wave forces considering phase differences.
2)　Computed amplitudes and periods of motions are agreed well with the results of experiment.
3)　Added masses and damping coefficients corresponding to significant wave period may be used in the computation of ship's motions in irregular waves.
4)　In the case force-deformation characteristic of mooring for sway motion is strong and also ship is subjected to waves but not to wind, long period sway motion occurs and the amplitude of sway motion to seaward becomes large.
5)　By the action of seaward wind, the neutral of ship's sway motion moves to make weak the asymmetry of mooring system. Consequently the period of ship's sway motion becomes nearly equal to wave period and also ship's sway motion becomes small.