The　barrier　anodic　alumina　membranes　with　good　insulation　performance　were　prepared　via　chemical　route　by　anodization　of　pure　Al　coatings,　1　μm　thick,　deposited　by　magnetron　sputtering　on　glass　substrates.　The　impacts　of　the　preparation　conditions,　including　the　compositions　of　the　electrolytes,　and　anodization　voltage　on　its　property　of　the　membrane　were　evaluated.　Its　microstructures　were　characterized　with　scanning　electron　microscopy　and　energy　dispersive　spectroscopy.　Under　the　optimized　conditions:　a　solution　of　95%　glycol,　1.9%　ammonium　sebacate,　and　3.1　boracic　acid,　the　high　quality　Al2O3　membrane　was　obtained.　The　measured　results　show　that　the　Al2O3　membrane,　a　few　nm　in　thickness,　possesses　an　excellent　insulation,　with　a　breakdown　field　of　5.25　MV/cm.