Pt nanoparticles (NPs) have been successfully encapsulated in SBA-15 mesoporous silica support. The silica was firstly functionalized by polyaminoamine (PAMAM) dendrimers with various generations and provided different nanometer space for Pt NPs. The growth of Pt NPs is restricted by the double confinement effect of PAMAM dendrimers and SBA-15 mesopores. The Pt NPs can be precisely controlled to localize inter- or intradendrimeric within SBA-15 tunnels. The different pore structures of Gn-PAMAM-SBA-15 (Gn-PS15) support have great influence on the catalytic performance of the encapsulated Pt NPs. The blocking structure of higher generation Gn-PS15 support debased the catalytic performance and increased the activation energy of reaction between Fe(CN)(6)(3-) and S2O32- in a certain degree. (C) 2011 Elsevier Inc. All rights reserved.