Spherical porous alumina (Al₂O₃) materials hold critical importance in industrial catalysis, but their direct synthesis remains a significant challenge. Herein, we report a hydrogen bond-enhanced monomicelle assembly strategy for synthesizing uniformly monodispersed mesoporous Al₂O₃ microspheres. This synthesis features the introduction of glycerol with abundant hydroxyl groups (−OH) to form the hydrogen bond network between the alumina-based monomicelles. The hydrogen bond network reduces the crosslinking rate of the Al₂O₃ oligomers and matches it with the micelle assembly rate, thereby enabling the direct synthesis of mesoporous Al₂O₃ microspheres in solution. The resultant mesoporous Al₂O₃ microspheres exhibit uniform spherical morphology (~ 1.3 μm), a high specific surface area (144 m²·g⁻¹), a large pore size (~ 7.8 nm), and abundant Lewis acid sites. Moreover, this strategy is universal for organic and inorganic Al₂O₃ precursors, overcoming the limitations of precursor compatibility. The mesoporous Al₂O₃ microspheres loaded with uniformly distributed PtSn nanoparticles are utilized as a highly efficient catalyst for propane dehydrogenation to propylene. The catalyst exhibits high propane conversion rate (~ 41%), high selectivity to propylene (> 98%), a low deactivation rate constant (0.004 h⁻¹) and remarkable long-term stability (~ 200 h) under industrial conditions at 550 °C.