This study focuses on the catalytic behavior of the Diesel Oxidation Catalyst using different aging characteristics of road mileage in order to improve the efficiency of an ammonia SCR system on an after-treatment line composed by a DOC + DPF + SCR. The studied catalyst is a commercial diesel oxidation catalyst (Pt/Pd/Al 2 O 3) provided by Continental. Hydrothermal aging were performed on carrots of monolith in varying the temperature of treatment. These carrots were characterized, X-ray diffraction (XRD), transmission electron microscopy (TEM) coupled by EDS and Specific surface measurement (S BET). The catalytic measurements consisted of series of temperature programmed surface reactions (TPSR). To be close to real driving conditions, our experimental setup comprised a pre-heater in which the gases were heated up to 500°C. The goal of this study is to understand the evolution of the active phase with the aging and to correlate these aging results with the corresponding overall catalytic activity and their impact on the reactions involved in the DOC with respect to CO, hydrocarbons and NO.