Cone-shaped hollow foundation is a new form of onshore wind power foundation, which has the advantages of low steel and concrete consumption and reduced waste soil generation during excavation of the foundation pit, compared with the traditional gravity foundation. In order to investigate the bearing characteristics of a cone-shaped hollow foundation under combined loads, a numerical simulation was carried out to investigate the influence of the ratio of the diameter of the top plate to the diameter of the bottom plate on the combined bearing capacity and damage mode of the foundation when the volume of the foundation is held constant. The results demonstrate that when the ratio of the diameter of the top plate to the diameter of the base plate is 6, the vertical ultimate bearing capacity of the cone-shaped hollow foundation is 100% higher than that of the same volume gravity circular foundation, and the moment ultimate bearing capacity is 60% higher. The failure envelopes of different diameter ratios of the cone-shaped hollow foundation can be described by a curve under different combination loads, and the expressions of the failure envelopes of different combination loads are proposed. The failure envelopes of gravity circular and cone-shaped hollow foundations under combined horizontal and bending moment loads show obvious asymmetry, with opposite directions of eccentricity. When the horizontal and bending moment loads are in different directions, the circular foundation has higher bearing capacity. When the horizontal and bending moment are in the same direction, the cone-shaped hollow foundation has higher bearing capacity. The cone-shaped hollow foundation shows a better combination of load-bearing capacity, which can be provided for the super-large single installed capacity wind turbine.