The development of highly stable propane dehydrogenation catalyst is significant with the growing extraction of shale gas in the world. A highly dispersed MnOx site decorated dendritic mesoporous silica nanoparticle support was prepared by simple in-situ emulsion method. It shows exceptionally ability to disperse and stabilize Pt clusters. The strong interaction between Pt and Mn formed and the electron transfer happened from Mn to Pt, which leads to an increase in the electron density of Pt. The high propane dehydrogenation activity, even for 100 h long-term test, was obtained on moderate Mn content catalyst. According to the experimental results and DFT calculation, the highly dispersed PtMn alloyed nanoparticles play an important role in enhancing the catalytic performance for propane dehydrogenation via a good balance on propane activation and propene desorption. (C) 2020 Elsevier Inc. All rights reserved.