Mesoporous alumina modified by silica (MA-S) with good thermal stability was prepared by a self-assembly method. The morphology and microstructure of as-prepared samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and so on. Though adding 5 wt% SiO2 in Al2O3 framework, the MA-S exhibited high thermal stability and large specific surface area (87 m(2) g(-1)) at 1200 degrees C. The results indicated that SiO2 can suppress the phase transformation from gamma-Al2O3 to alpha-Al2O3 and postpone the crystallization temperature at same time. Therefore, the as-prepared materials possess a great potential for application at high temperature.