In order to accurately predict the ship resonance dynamic stability of the shipboard helicopter, a nonlinear modeling and analysis method was proposed. According to the dynamic characteristics of shipborne helicopter free landing, the time domain load of ship to helicopter is considered in complex sea condition, the nonlinear dynamic characteristics of the rotor lag dampers, the blade flapping and aerodynamic forces are considered. The fuselage, rotor attenuator, blade flapping and lagging motion, and aerodynamic force are modeled separately as a submodel. According to the mechanics principle, the subsystems are integrated; an analysis model of the ship resonance is finally established. The methods of calculation and simulation test for ship resonance are presented. Using digital simulation technology, the driving test whole process of helicopter ship resonance can be displayed dynamically, simulating the excitation load of ship’s ups and downs, rocking motion to the fuselage, simulating the collective pitch control and the cycle excitation through the flexible driving lever actually. The stability of ship resonance can be analyzed, the transient response of dynamic system under the torsion is based on the time domain simulation. Finally, through the study of an engineering example, and the simulation test technique of accurately predicting the instability boundary for helicopter ship resonance is mastered. Providing design analysis method for the experiment which cannot be carried out in the development of model.