In this paper, we present a convenient hydrothermal method to synthesize hierarchical microspheres consisting of ammonium aluminum carbonate hydroxide (AACH) nanowires with a diameter of about 400 nm and length ∼50 μm on aluminum foils. After calcination at 900°C, hierarchical γ-Al 2 O 3 microspheres with mesoporous structures were obtained successfully, which possess a high specific surface area of 124 m 2 g −1 and high porosity of 0.71cm 3 g −1 . The possible formation mechanism was discussed. The as-prepared mesoporous γ-Al 2 O 3 hierarchical nanostructures exhibited improved adsorption performance towards Congo red in aqueous solution, 90% CR could be removed rapidly in 20 min, and its saturation adsorption capacity in 80 mg l −1 Congo red can reach to 180 mg g −1 , it suggests that the hierarchical γ-Al 2 O 3 microspheres with unique microstructure have potential in wastewater treatment.