The passive ammonia SCR system is a novel aftertreatment method for lean-burn engine to reduce NO_x emission and produce necessary ammonia for SCR. The reaction between NO and H₂ was activated and ammonia gas of SCR, denitration was then prepared under the action of a catalyst. Pd_0.01Cu_xCe_(1-x)/2Zr_(1-x)/2O_y catalysts with x parameter of 0, 0.1, 0.2 and 0.4 were synthesized through self-propagating combustion reaction method. The activities of catalysts were investigated according to XRD, BET, Raman, H₂-TPR, XPS, in situ DRIFTS. The relationship between the catalyst reactivity and species composition, acid property, and redox behavior was established in the end. The results showed that a moderate amount of Cu doping could significantly form more acid sites and tune the valence distribution of surface elements so as to lead to a high catalytic efficiency. Pd_0.01Cu_0.1Ce_0.45Zr_0.45O_x had the highest ammonia conversion rate among all the catalysts with a wide reaction temperature window of 225-375 ℃. The conversion rate of NO to NH₃ was beyond 90% with the catalyst due to the improved catalytic activity led by the fact that highly-dispersed CuO enhanced the interaction between CuO and Ce_0.5Zr_0.5O₂ carrier.