It is well known that the wave motion is a really complex process and hard to be simulated. The paper mainly solves the difficult problem of numerical simulation of wave disturbances in ship motion simulation area. The wave disturbance force and moment acting on the ship sailing on the sea are simulated. Based on statistics superposition theory, Pierson-Moskowitz (P-M) single-parameter standard wave spectrum is used to simulate a random long-crested sea wave. A kind of wave disturbance mathematical model is established, according to which the random wave disturbance force and moment acting on a large ship is calculated and simulated real time in the typical conditions of sea state 4. The influence of ocean wave to the large ship is also analyzed through the simulation research of the movement track and course change of the large ship under certain ocean waves. As the simulation results shown, the obtained wave disturbance force and moment is basically accorded with the real situation. At the same time, it shows that the ocean wave has great influence on 4 degree of freedom (DOF) large ship, which can't be ignored in engineering research. To some extent, the established wave disturbance mathematical model may contribute to the further research on the area of ship motion and offshore operation.