Abstract: With the aggravation of energy shortage and environmental pollution, the development and utilization of renewable energy have become the focus of research in countries around the world. As a green renewable energy source, offshore wind energy is one of the effective ways to solve these problems. The foundation form of built offshore wind farms is mainly large-diameter monopile. With the development of offshore wind farms expanding toward the deep sea, the applicability of the large-diameter monopile is confronted with some significant challenges. The exploration and research of a new type of foundation are important and meaningful. Affected by the weight of the superstructure and the load of the marine environment, the design of offshore wind turbine foundations should consider the bearing performance of the foundation under vertical load, horizontal load, and bending moment. The ABAQUS software was used to compare the bearing capacities of large-diameter monopile, pile–plate composite foundation, and pile–bucket foundation in saturated clay under vertical load V, horizontal load H, and bending moment M. Results show that the bearing capacities of the two composite foundations are better than the bearing capacities of the monopile foundation. The vertical, horizontal, and bending bearing capacities of pile–plate composite foundations increase exponentially with the increase in the diameter of the plate. The vertical and bending bearing capacities of the pile–bucket foundation increase with the increase in the buried depth of the bucket structure increasing, and the increasing trend gradually weakens parallel to the line. The horizontal bearing capacity of the pile–bucket foundation has a linear relationship with the diameter and buried depth of the bucket structure in the soil. Under the composited loading conditions of V–H and V–M, the failure envelope spaces of the two composite foundations are larger than those of the monopile, and the bearing performance of the two composite foundations is significantly better than that of the monopile.