An ultrahigh heat-conduction metal-based circuit board and a fabrication method thereof belong to the field of a power module. The metal-based circuit board comprises a substrate layer, a composite heat conduction insulation layer and a conductive circuit layer, wherein the composite heat conduction insulation layer and the conductive circuit layer are attached onto the surface of the substrate layer according to a sequence, and the composite heat conduction insulation layer is prepared from Al2O3 and hydrates thereof of Al<2>O<3>.2H<2>O and Al<2>O<3>.3H<2>O. The metal-based circuit board is simple in structure, the composite heat conduction insulation layer has favorable heat conduction performance and insulation performance, the heat conduction performance is over 100W, heat transfer is met, and meanwhile, and the defects such as low breakdown voltage, low stripping strength and non-uniform thickness of a conductive circuit are overcome; and moreover, the fabrication method of the metal-based circuit board is simple and efficient, is low in cost and is easy for promotion and application.