Liquid fuel reforming is an efficient way to produce hydrogen for mobile fuel cell systems. However, the catalyst is easily damaged by coke formation and thermal sintering during the reaction. In this study, an exsolved PtRu alloy catalyst was investigated for hydrogen production via diesel reforming. The crystal structure, electronic state, and surface morphology of the catalyst were analyzed by XRD, XPS, and TEM. The energetics for the exsolution of metals and their surface alloy formation were also predicted based on DFT calculations. The asprepared catalyst was found to be a solid solution where Pt and Ru were incorporated into a CeO2 lattice. During the reaction, Pt and Ru were exsolved from the support to form PtRu alloy nanoparticles. Synergistic effects were observed in the PtRu alloy catalyst. It showed improved activity and stability with high resistance to coke formation and thermal sintering compared to monometallic Pt and Ru catalysts.