Hollow mesoporous silica (HMS) decorated with fine Pt nanoparticles is directly prepared through a dual soft-template system using a triblock copolymer, poly(styrene-b-2-vinyl pyridine-b-ethylene oxide), and a cationic surfactant, cetyltrimethylammonium bromide. The Pt nanoparticles of uniform particle size are stably embedded inside the mesoporous silica shell and possess both a huge surface area and a large total pore volume. The Pt nanoparticles supported by the mesoporous silica exhibit excellent thermal stability, which enables their application in high-temperature CO oxidation.