Abstract: Ship-helicopter coupled unsteady flowfield are complicated and disordered, and the six-degree-of-freedom motion of the ship will further worsen the flowfield environment above the flight deck. This paper conducted numerical simulations of the pitching ship-helicopter coupled flowfield under two kinds of oblique wind conditions by computational fluid dynamics (CFD) method using the model of simplified frigate SFS2 and rotor. The influence of the pitching motion on the coupled flowfield structure and rotor’s thrust is analyzed, and the differences in the flowfield under the two conditions are compared. Results show that, with the pitching motion of the ship, the unstable mixed vortical structures and vertical airflow formed behind the hangar will affect the rotor's aerodynamic force. The rotor’s thrust changes approximately periodically, consistent with the pitching motion period, but the velocity components at each observation point do not. The rotor’s thrust is maximum when the deck goes up to the horizontal position and minimum when the deck sinks to the horizontal position. For the port and starboard wind, the thrust decreases by about 13% and 6%, respectively. Therefore, pilots should be aware of the thrust loss caused by the pitching motion, ensure that the helicopter has enough operating margin, and timely adjust the collective pitch to enhance the helicopter’s take-off and landing safety in this situation.