We propose H₂-D₂ titration method for evaluation surfaces of metallic catalysts, and have been applied to a study on the surface reconstruction of Pd foil model catalysts modified by the UHV treatment for H₂-D₂ exchange reaction. The UHV treatment brought about the reconstructed surfaces of Pd foil catalysts, and the improvement of H₂-D₂ exchangeactivity and the decrease of activation energy. The H₂-D₂ titration over the UHV-treated Pd foil catalysts indicated that the number of strongly adsorbed hydrogen atom species was increased by the UHV treatment. These results strongly suggest that the UHV treatment generates the newly active sites on Pd foil catalysts. The SEM study also supported the surface reconstruction of the Pd foil catalysts by the UHV treatment. In this report, we introduce the high sensitivity of the H₂-D₂ titration for hydrogen activation sites over a low surface area metallic catalyst.