A dual-inlay preparation method for using hard cover curtain of metal includes semiconductor substrate consisting of a conducting wire structure, a dielectric separation layer, a dielectric layer of low dielectric constant, a first and a second hard cover curtains of metal, forming a first opening on the second hard cover curtain and a second opening on the first one with the second opening belowthe first one as the bore of the second opening smaller than the first one, rewoving off dielectric layer being not covered by the first hard cover curtain until an interlayer hole being formed as the dielectric separation layer to the exposed and furthermore forming, a ditch above the into layer hole by removing the dielectric layer off to the preset depth after the first hard cover curtain which is not covered by the second one to have been removed off.