In this study, the effect of the flow behavior on degradation of a de-NOx catalyst is experimentally and numerically investigated. The results show that the degradation of the de-NOx catalyst is remarkably affected by the inner flow behavior, namely turbulent-laminar flow transition. The degradation of the catalyst is enhanced in the upstream region near the inlet, since injected turbulent flow facilitates particles in flue gas to adhere the catalyst surface. In the downstream region, on the other hand, the degradation of the catalyst is gentle. This is due to the fact that the inner flow varies from turbulent to laminar flow toward downstream, which prevents particle from adhesion to the surface. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.