Fe-ZSM-5 with particle size of 200 nm was coated with a tiny silicalite-1 shell via secondary hydrothermal crystallization in order to improve the hydrophobicity of Fe-ZSM-5 on NH3-SCR. The formation mechanism, adsorption performance and SCR activity of the core-shell zeolites were investigated in this paper. During the secondary hydrothermal crystallization procedure, the different content of silicon source (TEOS) led to the different morphologies of the shell. Comparing to Fe-ZSM-5, the core-shell zeolites have higher activities on NH3-SCR and hardly impacted with H2O. For a further study, UV-Vis DRS, TPD, in situ FTIR and TG were combined and suggested that the differences between Fe-ZSM-5 and core-shell zeolites on NH3-SCR performance can be attributed to the adsorption of NOx on silicalite-1, Fe species transformation during secondary hydrothermal crystallization and the hydrophobicity of silicalite-1. (C) 2014 Elsevier B.V. All rights reserved.