This paper presents a frequency domain (FD) approach for analyzing wind and wave coupling effect on motion responses of an integrated offshore fish cage and wind turbine named COSPAR. FD analysis was performed by ANSYS AQWA to obtain response amplitude operators (RAOs) for surge, pitch and heave motions as well as mooring tension RAOs. Wind thrust was estimated by using a linearization method based on the pre-defined thrust coefficients determined from a fixed-bottom wind turbine. In AQWA, wind force coefficients were specified to incorporate the thrust force and moment in the hydrodynamic response analysis of a floating structure. The present FD method was applied to a DeepCwind floating wind turbine problem for its validation. It was found that the AQWA-FD approach can furnish wind and wave induced motion responses that are comparable with published experimental and numerical results. Thereby, this approach can be used to readily obtain a preliminary design for subsequent refinements for an optimal design. Based on the FD analysis results, DeepCwind and COSPAR have a pronounced the coupling effect only in the pitch motion. Moreover, COSPAR shows not only moderate coupling effect, but steadier and less RAOs in surge, heave, pitch and mooring tension than those of DeepCwind. In addition, it is evident that COSPAR can provide a stable working platform for offshore fish farms from wind, wave and current loads, and has acceptable pitch angles for a steady wind turbine operation.