A coupled time-domain simulation model for the Submerged Floating Tunnel (SFT) was established in OrcaFlex to investigate the influence of key parameters on the dynamic response of an elliptical cross-section SFT under wave-current interactions, employing a "tunnel tube + 6D buoy" approach. Both the tunnel and anchor cables were represented using finite element line models that capture elastic deformation capabilities. These line models consist of massless axial, bending, and torsional springs, along with concentrated mass points connected by massless springs. The tunnel and anchor cables were linked using a dummy-connection-mass method. Under the extreme wave and current conditions of the Taiwan Strait, the study examined how structural parameters such as anchor cable arrangement, buoyancy-to-weight ratio (BWR), and submerged depth affect the dynamic response of the SFT. Findings indicate that, the torsional motion of the tunnel tube is effectively mitigated under the coaction of both waves and currents when the sum of the anchor cable installation angle and inclination angle equals 90°. Furthermore, under the "four-inclined non-cross-mooring" cable arrangement, the amplitudes of sway and roll motions of the tunnel tube were significantly lower compared to those of the "four-inclined cross-mooring" arrangement. Additionally, a synergistic relationship was observed between the BWR and the submerged depth. When the submerged depth is small, a larger BWR can ensure the stability of the SFT; whereas for larger submerged depths, a smaller BWR can effectively prevent the fatigue damage of the anchor cables from being subjected to large repetitive stresses.