Pt/BaO/Al2O3was used for NSR study as NOx storage catalyst, which was included in the exhaust gas from diesel engine. Bridging nitrate found from 1592 cm-1 and 1626 cm- 1 during lean period appeared to be removed during rich period. Bridging nitrate and monodenate nitrate were measured over Pt containing catalyst. During rich period, monodenate was not removed while bridging nitrate was disppared.