The mooring property is an important factor affecting the motion of the mooring ship. Based on the MIKE 21 Mooring Analysis numerical simulation software，a 177，000 m3 LNG ship is subjected to a numerical mooring test under the action of irregular transverse waves，and its influence on the motion of the moored ship is analyzed by changing the diameter and material of the rope. The results show that：1）The motion of the mooring ship is affected by the material and diameter of the rope，mainly due to the change of the rope stiffness. 2）The sway，surge and yaw movement of the mooring ship are greatly affected by the change of the rope，and all decrease with the increase of the rope stiffness. 3）The heave is mainly related to the incident wave period and wave height，and is less affected by the stiffness of the rope. 4）Pitch has little change due to its small amount of motion. 5）There is no obvious change rule for roll relative to the change of rope stiffness.