A facile hydrothermal and thermal decomposition route was used to synthesize the alumina microrods with mesoporous structure. The as-synthesized products were characterized with use of Raman spectroscopy, XRD, SEM, thermal analysis and N2 adsorption-desorption measurement. Formation of the ammonium aluminium carbonate hydroxide phase was ascertained to be an indispensable condition for formation of alumina micro-rods. Thermal decomposition of ammonium aluminium carbonate hydroxide was shown to afford formation of amorphous alumina microrods. These microrods are microporous-structured and crystallize as γ-Al2O3 at temperatures over 800 °C. With gases burning out, mesopores are formed with the amorphous alumina framework.