Provided are a method of preparing a metal oxide-silica composite aerogel which includes preparing a silicate solution by dissolving water glass at a concentration of 0.125 M to 3.0 M, after adding and mixing a metal salt solution having a metal ion concentration of 0.125 M to 3.0 M to the silicate solution, precipitating metal oxide-silica composite precipitates by adjusting a pH of a resulting mixture to be in a range of 3 to 9, and separating and drying the metal oxide-silica composite precipitates, wherein the metal salt solution includes a magnesium (Mg)-containing metal salt in an amount such that an amount of magnesium ions is greater than 50 mol % based on a total mole of metal ions in the metal salt solution, and a metal oxide-silica composite aerogel having low tap density and high specific surface area prepared by the method.