Abstract: We report the synthesis of ordered mesoporous ceria (mCeO₂) with highly crystallinity and thermal stability using hybrid polymer templates consisting of organosilanes. Those organosilane-containing polymers can convert into silica-like nanostructures that further serve as thermally stable and mechanically strong templates to prevent the collapse of mesoporous frameworks during thermal-induced crystallization. Using a simple evaporation-induced self-assembly process, control of the interaction between templates and metal precursors allows the co-self-assembly of polymer micelles and Ce³⁺ ions to form uniform porous structures. The porosity is well-retained after calcination up to 900 C. After the thermal engineering at 700 C for 12 h (mCeO₂-700-12 h), mCeO₂ still has a specific surface area of 96 m² g^-1 with a pore size of 14 nm. mCeO₂ is demonstrated to be active for electrochemical oxidation of sulfite. mCeO₂-700-12 h with a perfect balance of crystallinity and porosity shows the fastest intrinsic activity that is about 84 times more active than bulk CeO₂ and 5 times more active than mCeO₂ that has a lower crystallinity.