The invention discloses a method for preparing a composite insulation layer on the surface of an aluminum alloy battery shell. The method for preparing the composite insulation layer on the surface of the aluminum alloy battery shell is characterized by specifically comprising the following steps that firstly, the surface of the aluminum alloy battery shell is cleaned with a cleaning agent, so that greasy dirt is removed, and pretreatment of the surface of the aluminum alloy battery shell is completed; secondly, a micro-arc oxidized ceramic layer is prepared on the surface, pretreated in the first step, of the aluminum alloy batter shell; and thirdly, polymethyl and phenyl organic silicon resin and absolute ethyl alcohol are mixed for obtaining organic silicon resin spraying liquor, and the micro-arc oxidized ceramic layer obtained in the second step is sprayed with the organic silicon resin spraying liquor and solidified, so that the composite insulation layer is prepared on the aluminum alloy batter shell. By adoption of the preparation method, the composite insulation layer can be formed on the surface of the aluminum alloy batter shell, and thus the insulation property of the surface of the aluminum alloy batter shell can be improved.