Abstract: At present, research on the wave and current forces acting on offshore wind turbine foundations mostly focuses on monopiles, with simulation models often simplified as smooth cylinders of constant diameter that neglect ancillary components. Moreover, simulated sea conditions are typically limited to simple waves that disregard currents. However, in actual marine environments, offshore wind turbine foundations are subjected not only to wave action but also to continuous ocean currents, with the directions of waves and ocean currents forming constantly changing angles, and the water depth is constantly changing. While monopiles are predominantly utilized in shallow waters, the expansion of offshore wind power projects into deeper waters has led to the increasing prevalence of high pile cap and jacket foundations, which are more suitable for deep-water areas are also becoming increasingly prevalent. To understand the wave-current force characteristics of different foundations of offshore wind turbines under actual sea conditions, this study takes three types of fixed foundations (monopile, high pile cap, and jacket), including attached components, as research objects. The effects of wave height, water depth, and wave-current angle on the forces acting on these three foundations under combined wave-current action were studied through physical model experiments. The experimental results were then compared with the calculated values derived from the Morison formula. The results show that: (1) Under the combined action of waves and currents, the influence of wave height, water depth, and the angle between wave and current on the total horizontal force of each foundation varies, with wave height having the most significant impact, followed by water depth and then wave-current angle. In general, greater wave height and deeper water depth correspond to larger total horizontal forces on the foundation. The effects of wave height and wave-current angle on the wave-current forces of monopiles are more significant than on high pile caps and jacket foundations, while the influence of water depth on the wave-current force of high pile cap foundations is more pronounced than that on monopiles and jacket foundations. (2) The maximum total horizontal force on the foundation model does not occur when wave and current directions are aligned, but rather when there is a certain angle between them. The wave-current angle corresponding to this maximum force varies under different operating conditions, with the majority occurring at a wave-current angle of approximately 45° or 90°, and a minority at 22.5°. Theoretically, the linear superposition of wave and current forces is greater when the wave and current directions are aligned than when there is an angle between them, but the actual phenomenon does not align with theory. This may be related to the influence of various accessory components of the foundation, since their presence both increases the effective action area of waves and currents on the foundation, and simultaneously causes waves and currents in different directions to couple and superimpose, thereby forming a more complex and enhanced flow field that increases the loads on the foundation. In practical engineering design, the Morison formula is primarily used for calculating wave-current forces. By comparing the experimental results with the Morison formula’s values for wave-current forces in the same direction, a wave-current angle amplification factor is introduced: 1.23, 1.14, and 1.17 for monopile, high pile cap, and jacket foundations, respectively. This factor ensures structural safety without being overly conservative. This article reveals the influence of the wave-current angle on wave–current forces. The maximum horizontal force occurs when there is a certain angle between the wave and the current, which has guiding significance for structural optimization design in complex wave-current environments. By proposing an amplification factor for the wave-current angle based on experimental data, designers can reasonably consider the influence of the angle when calculating wave-current forces, achieving a balance between safety and economy, and avoid overly conservative designs.