The method of formation carried out hydration treatment for aluminum foil after process of electrolytic corrosion in 95% or more pure water. Characters are that after hydration, formation in second time is carried out in water solution with density 0.05%-0.5% of ammonium pentaborate and density 1-10% of boric acid at 60-90 deg.C; then depolarization process is carried out; after depolarization process, dipping in formation liquid is carried out for aluminum foil in water solution with density 0.05%-0.2% of ammonium pentaborate and density 1-10% of boric acid. Useful effects are: simple practical technique, high quality of production, and reducing 20-30% leakage current of electrode foil.