Gyroscopic motion is considered as an appropriate approach to suppress the shaking motion of rigid bodies. Its spatial orientation is also used to make gyro compasses in the marine industry. In this paper, the floating offshore wind turbine (FOWT) was designed based on potential theory and gyroscopic effect and rotational axis retention effect were also considered, so that FOWT could obtain better hydrodynamic response. However, gyroscopic motion was generated through an annular flow in the internal torus instead of rigid body rotation. The scale of torus and the angular velocity of the annular flow were the design parameters that this article was eager to understand obviously. By vast quantity of calculations, the suitable range of design parameters was obtained.