By simple chemical etching method, prepared aluminium alloy substrate surface of hydrophobic membranes. After infiltration oxidation by potassium permanganate solution and treatment with stearic acid of low surface energy, the etching aluminium surface has the properties of super-hydrophobic. SEM analysis of the aluminium alloy surface shows that the surface develops the micro-nano structure, which played a key role to the super-hydrophobic properties. In the experiments, studies the effects of different kinds of acid, different etching time and different etching concentration on the hydrophobic membranes. The best preparation conditions are: mixed solution of 0.08 mol/L oxalic acid and 1 mol/L hydrochloric acid etching for 15h, then 0.1 mol/L of potassium permanganate solution soaking for 1h, finally 1% stearic acid ethanol solution soaking for 30min, meanwhile the contact angle of water droplets with the surface up to 166 °.