The invention provides an anisotropic composite material for a spaceborne radar antenna panel, and a preparation method thereof, and relates to a composite material for a spaceborne radar antenna panel, and a preparation method thereof. In the prior art, the existing composite material for spaceborne radar antenna panels can not concurrently meet a transverse tensile strength and longitudinal tensile strength, and has characteristics of poor comprehensive mechanical property and not high density. A purpose of the present invention is to solve problems in the prior art. The composite material is prepared from 60-80% by mass of an asphalt base graphite fiber reinforcement body, 4-6% by mass of aluminum nitride particles, and the balance of a matrix aluminum alloy. The preparation method comprises: coating an aluminum nitride suspension on the surface of fibers, fixing into a bundle, injecting an aluminum alloy solution to impregnate, and spraying a cooling liquid to rapidly cool to obtain the composite material. The anisotropic composite material has characteristics of high density, high longitudinal tensile strength maintaining, high longitudinal thermal conductivity maintaining, transverse tensile strength increase, transverse thermal conductivity increase, and excellent comprehensive performance, and can be used in the field of spaceborne radar antenna panels and preparations thereof.