The influence of the introduction of Pt and/or Fe on the structures, NO x storage property and sulfur removal performance of Ba/Al 2 O 3 catalyst was studied. The techniques of TG/DTA, XRD, FT-IR, H 2 -TPR, EXAFS and DRIFTS were employed for the careful characterization of the catalysts. Two types of Ba species are identified, namely a well-spread monolayer of Ba species and a bulk BaAl 2 O 4 phase. The addition of Fe inhibits the Ba dispersion by enhancing the bulk BaAl 2 O 4 formation, thus slightly decreasing the SO x absorption and greatly suppressing the growth of the bulk BaSO 4 , and its addition also promotes the NO x storage by increasing the mobility of the stored NO x , contributing to the formation of bulk Ba(NO 3 ) 2 . The introduction of Pt always re-disperses the bulk BaAl 2 O 4 phase via a hydration process, and enhances both the NO x and SO x absorption capacity of the catalyst. Whereas the co-existence of Pt and Fe was detrimental for the NO x storage and sulfur removal as compared with Pt/Ba/Al 2 O 3 catalyst, although it favors the reduction of BaSO 4 phase. Based upon the EXAFS, in situ DRIFTS and repeated H 2 -TPR results, it is found that the interaction between Pt and Ba species is of great importance for NO x storage and sulfur removal. This Pt–Ba interaction not only accelerates the NO x spillover which is a key step during storage, but also facilitates the selective reduction of BaSO 4 into H 2 S, favorable to sulfur removal and catalyst regeneration. The introduction of Fe to the Pt/Ba/Al 2 O 3 catalyst decreases this Pt–Ba interaction by encapsulation of Pt in the matrix of Fe/FeO x lattice after repeated redox cycles, leading to the decrease of NO x storage capacity (NSC) of the catalyst, and making sulfur removal more difficult since Fe selectively catalyzes the reduction of BaSO 4 into BaS.