Reduction and carburization behaviors of iron phases over a precipitated iron-based Fischer-Tropsch synthesis (FTS) catalyst were investigated by some techniques of Massbauer effect spectroscopy (MES), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) as well as H-2&CO temperature-programmed desorption (H-2&CO-TPD). It was found that in H-2 atmosphere phase transformation of iron phases involved alpha-Fe2O3 -> Fe3O4 -> FeO -> alpha-Fe, both occurring in the bulk and on the surface layers. All of reduced iron species took place the carburization reaction, whereas carburizing ability was following the order alpha-Fe > FeO > Fe3O4. During FTS both iron carbides and Fe(II) oxide species reached a balance state without appearing the intermediate alpha-Fe. The conversion of reduced iron phases to iron carbides (especially for x-Fe5C2) on the surface layers played a positive role in promoting the formation of hydrocarbons species. (C) 2014 Elsevier Ltd. All rights reserved.