Employing NH4HCO3 as pore-enlarging agent and P123 as a template agent, ordered mesoporous Mg-doped gamma-Al2O3 with different basicity and large surface area have been successfully synthesized by a facile sol gel approach by adjusting the content of magnesium and pH value. Specifically, the result alumina calcined at 1000 degrees C with large specific surface area (234.4 m(2) g(-1)) and high pore volume (0.72 cm(3) g(-1)) was obtained when the Mg content was 9 wt %. These materials with ordered mesostructure and advantageous structural properties were utilized as carriers of Pd-Al2O3 catalysts for the catalytic reaction of simulated exhaust automobile gases including CO, NO, and hydrocarbon (HC). The results revealed that the high catalytic performance of Pd/9Mg-OMA originated from its more appropriate basicity, greater PdO dispersion, and higher surface area.