Objective: Floating vertical-axis wind turbines (VAWTs) hold a massive potential for rapid advancements in the coming years owing to their relatively low cost of energy. To date, very few studies have analyzed the dynamic response characteristics of floating VAWTs using wave basin model tests. Only some studies have specifically focused on the strain responses of blades and struts of floating VAWTs. In the present study, a 5-MW floating VAWT concept, which consists of a three-bladed rotor and a semi-submersible platform, was proposed. This study aims to elucidate the response characteristics and the factors affecting the wind turbine under combined wind and wave conditions. The outcomes of the study contribute to the advancement of floating VAWT model test technology. Methods: The dynamic response characteristics of this wind turbine were investigated using a wave basin model test at a 1∶50 scale. Based on the actuator cylinder model and least squares fitting correction, a performance-scaled rotor was designed to match the target thrust and lateral forces. A fiber Bragg grating (FBG) sensor-fiber optic rotary joint (FORJ) strain sensing system was integrated into the driving and supporting device for the wave basin model test of floating VAWT to monitor the strain responses of blades and struts. Subsequently, a series of preliminary calibration experiments, including wind and wave calibration tests to validate the environmental conditions, thrust calibration to evaluate whether the designed performance-scaled rotor can produce the expected thrust and side forces, and a six-degree-of-freedom free decay test in calm water to validate the physical model system, were conducted. Additionally, a rotating test was performed to study the feasibility of the developed FBG-FORJ strain sensing system. Finally, a 1∶50 model test was conducted under wave-only, wind-only, and combined wind-wave conditions. The experimental results are thoroughly analyzed, with a specific focus on the dynamic responses of global motions, tower-base sectional loads, mooring line tensions, and the strain responses of blades and struts. Results: The results show that the designed performance-scaled rotor can reproduce the thrust and lateral force of the prototype wind turbine. The strain-measurement system exhibits high sensitivity, and it can effectively capture the strain variations induced by external excitations. In the rotating tests, the first flap-wise bending mode of the blade is excited by the centrifugal force that is acting on the blade. Conclusions: This study provides valuable insights into the dynamic behavior of floating VAWTs under combined wind and wave conditions. The mean values of the platform's surge and pitch motions are mainly affected by wind loads, while their fluctuations are affected by wave loads. Additionally, aerodynamic damping effects persist in surge and pitch motions. The mean values and fluctuations of the tower-base bending moment and the mooring tension are affected by the aerodynamic load, and the 3P (three-times-per-revolution) component is dominant. The strain responses of the blades and struts are predominantly affected by wind loads, with the effect of wave loads being minimal. According to the current sensor configuration, the blade strain response and strain response of struts are mainly affected by the 1P (once-per-revolution) component and the 2P (twice-per-revolution) component, respectively.