Ammonia (NH3) slip from denitration (deNO(x)) process has been increasingly concerned due to the recent findings that NH3 played an important role in promoting the formation of haze. Considering the hightemperature and humidity application conditions of diesel exhaust and the location of NH3-SCO system, Pt/Fe/ZSM-5 catalyst was selected. In this work, Pt-Fe/ZSM-5 catalysts with two different Si/Al ratios (25, 50) were prepared through ion-exchange method and the NH3-SCO activity were compared both in dry and wet (5% H2O) circumstances. The Si/Al 25 sample exhibited higher intrinsic activity (dry circumstance) than the Si/Al 50 sample. However, with H2O addition the activity of Si/Al 25 sample decreased dramatically while Si/Al 50 sample maintained higher level. BET, XRD, XPS, H-2-TPR, NH3-TPD and in situ DRIFTS characterization results showed that abundant metallic Pt (Pt degrees) was beneficial to NH3-SCO activity, strong acid site determined the waterresisting property of the catalysts during NH3-SCO with H2O participation.