The diesel oxidation catalysts (DOC) having high purification performance to the exhaust gas at low temperatures were investigated. In this paper two main technological improvements from conventional DOC are shown. First is forming Pt/Pd composite particles in order to suppress sintering of precious metal under high thermal aging condition. This generating Pt/Pd composite and the effect were exemplified by TEM-EDS and XRD analysis. Second is adjusting electric charge of Pt/Pd surface to reduce interaction between Pt/Pd and carbon monoxide (CO) by modifying the support material components. Adjusting electric charge of Pt/Pd surface by applying new support material could cancel CO poisoning at Pt/Pd surface. Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) studies suggested that improved support material is more suitable for CO oxidation at a low temperature based on the concept.In this study, the fundamental function of DOC such as oxidation activity at a low temperature and heat-up property by fuel injection were eventually evaluated using diesel engine. The new DOC achieved the performance competitive with conventional DOC applied for EU5 regulation, even if precious metal amount was reduced by more than 30 %, in terms of light off activity and fuel heat-up property after thermal aging at 800°C.