Magnesium oxide aerogels were made by sol-gel process using magnesium methoxide as precursor, methanol and deionized water as solvent followed by supercritical drying with respect to ethanol.The influences of the different factors on the gel time and the specific surface area of magnesium oxide aerogels are studied, and the structure and morphology were characterized by Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Transmission Electron Microscope (TEM) and X-ray diffraction (XRD), and the Small Angle X-ray Scatter (SAXS) was utilized to determine the fractural structure of the magnesium oxide aerogels.The results show that MgO aerogels belong to the typical mesoporous materials with rich network and highly developed pore structure, and the maximum specific surface area is 904.9 m2·g-1, the density is 0.055 g/cm3, the average pore size is 19.6 nm.The results of SAXS analysis show that the fractal dimension of the MgO aerogels is 2.32 in high q area which proves the existence of rough surface, and the calculated pore size distribution by SAXS is consistent with BET test.