Abstract: During the process between launch and water-exit, sub-launched missile will suffer wave forces, and the wave forces will affect the missile water trajectory parameters to a considerable degree. A random wave model was built using the Pierson-Moscoswitz spectrum and the SWOP direction distributing function, furthermore, equations for calculating wave forces were derived in reference of the section-cutting theory. According to the characteristics of the wave randomness, a series of statistical simulation were carried out by using the Monte Carlo like method. The rules of wave effect to the maximum parameter deviations of the uncontrolled ballistics with the variation of depth were obtained, and maximum ballistics parameter deviations of different sea conditions and wave angles were given, with the changing law described. The simulation method and results have a certain reference value for engineering studies.