Oscillatory behavior of the selective catalytic reduction of NOx by hydrogen (H-2-SCR) was studied over Pt/HY catalyst. It was found that the oscillation frequency increases with the increase of catalyst amount, reaction temperature and the H-2 concentration in the feed gas within the range of tested experimental conditions. The NOx-TPD indicates that the adsorption-desorption of NOx on Pt particles is involved in the oscillation. It is proposed that the primary surface species on the Pt particle is alternatively changed between Pt-NOx and Pt-H, and the oscillatory behavior of the H-2-SCR is a statistic result of oscillations on many Pt particles. The in situ FTIR and NH3 pulse injection studies reveal that NH3 is involved in the synchronous oscillation. (C) 2013 Elsevier B.V. All rights reserved.