Membrane technology has become a highly efficient separation technology for industrial applications over the past few decades. Compared to traditional membrane materials, alumina membranes are particularly significant for industrial wastewater treatment. However, the development of mesoporous α and γ-alumina (Al₂O₃) membranes for ultrafiltration applications is still a challenge due to uncontrolled pore size and low permeability, respectively. In this study, first, we optimized the sol-gel method for the fabrication of a high-performance mesoporous α-Al₂O₃ membranes. The peptization conditions (pH and peptization time) and phase transformation of boehmite were investigated to achieve better properties of the α-Al₂O₃ membrane. An α-Al₂O₃ ultrafiltration membrane with a pore size of 12.5 nm (MWCO=163 kDa) was obtained. This is the smallest pore size ever reported for pure α-Al₂O₃ membranes. Second, the properties of the γ- Al₂O₃ mesoporous membranes, sintered at 600 °C, were greatly improved by a modified sol-gel method using polyvinyl alcohol as an additive. The analysis revealed that the thickness of γ-Al₂O₃ membrane decreased as the concentration of PVA increased in the boehmite sol. The results showed that the porosity and surface area of the γ-Al₂O₃ membrane increased considerably using modified method. The γ-Al₂O₃ membrane fabricated via a modified sol-gel method with a pore size of 2.7 nm (MWCO=5300 Da) exhibited a pure water permeability of over 18 LMH/bar, which is three times higher than that of the γ-Al₂O₃ membrane prepared using the conventional method. Finally, the optimization of sol-gel method proved to be promising for preparing the high-performance Al₂O₃ multichannel tube-type mesoporous membranes.