In this research, a modular system is preliminarily developed to estimate motion responses of wind floats with the quasi-static mooring loads in waves. The modular system consists of the hydrodynamic simulator and the BEM (Boundary Element Method) solver based on the 3D source-distribution method. Specifically, the hydrodynamic simulator can be divided into three modules, including body element module, constraint module and global reference frame module, respectively. Subsequently, an indicator, Response Amplitude Operator (RAO), is suggested to present the resonance frequencies of wind floats for determining stability and safety in the operational sea state. In addition, it can be used to realize the contribution of the mooring load to the six Degree-of-Freedom (6 DOF) motions at the resonance frequency, and be considered as the design concept of mooring lines. In case of the mooring load, our model results are reasonably in agreement with other published data of numerical simulations. Eventually, a modular system developed by the software, Simulink, would be compared to the present hydrodynamic models for verifying its capability.