In situ surface Raman spectroscopy was used for investigation of induced-electrodeposition of Fe-Mo alloy. The results of Raman spectra showed that in the electrolyte without FeSO4, the Mo(VI) species reduction occurred at a potential more negative than -0.5 V (vs SCE) as indicated by the appearance of a new peak (ca. 730 cm(-1)) which corresponded mainly to a Mo(IV) species. The broadening of the peak was attributed to a Mo(IV) species deposited on the electrode surface existing in the form of a ＇molybdenum blue＇ compound. This compound was not further reduced even at the potential up to -1.9 V, while in the case where FeSO4 coexisted in the electrolyte, the formation of the molybdenum blue＇ became easier and the peak blue shifted to 740 cm(-1). Moreover, this peak faded away gradually in the potential region from -1.5 to -1.9 V and a bright Fe-Mo alloy deposited on the electrode surface was observed. These results showed that in situ surface Raman spectroscopy was a useful tool in the study of the induced-electrodeposition of this alloy.