A porous microsphere and a method for preparing the same includes the following steps. A copolymer having a vinylbenzyl chloride unit and a vinylbenzyl alcohol unit is dissolved in an organic solvent, and inorganic particles are dispersed in the organic solvent to form a mixed suspension. An aqueous solution containing a surfactant is provided. The mixed suspension is emulsified in the aqueous solution to form an emulsion. The emulsion is heated to evaporate the organic solvent to obtain inorganic-composite porous microspheres suspended in water. The copolymer in the formed porous microspheres can be further carbonized or removed to produce inorganic-based porous microspheres containing carbon or not containing carbon.