Alumina has recently turned out to be effective in enrichment of biomacrolecules like phosphopeptides due to its good affinity to phosphor groups. Ordered mesoporous alumina (OMA) materials with high surface areas, regular porous structures, and large pore size are an ideal absorbent for the enrichment of phosphopeptides. Herein, a ligand-assisted solvent evaporation induced coassembly route is developed to synthesize OMA materials with an ultralarge pore size (16.0-18.9 nm) using a high-molecular-weight poly(ethylene oxide)-b-polystyrene (PEO-b-PS) as a soft template, aluminum acetylacetonate as a precursor, and tetrahydrofuran as a solvent. The obtained ordered mesoporous alumina shows high surface area (114-197 m2/g), large pore volume (0.16-0.34 cm3/g), and high thermal stability (up to 900 °C). The OMA materials show crystalline γ-Al2O3 frameworks with crystal size of ∼11 nm after calcination at 900 °C in air. Because of their high surface area, ultralarge pore size, and rich Lewis acid sites, the obtained OMA materials are demonstrated to be an excellent bioabsorbent in enriching phosphopeptides selectively from protein digestions with ultralow concentrations (2 × 10-9 M), even from more complex samples from human serum.