We herein present an efficient approach for the chemoselective synthesis of arylamines from nitroarenes and hydrazine over an iron-molybdenum sulfide catalyst ([FeMo]Sx). The heterogeneous hydrogen transfer reduction can be efficiently carried out at 30 °C and provides anilines with 95-99% selectivities. The in situ gas product analysis demonstrates that [FeMo]Sx can catalyze the decomposition of N2H4 to H* species, not H2. Combining with the kinetic analysis of the aniline generation rates from nitrobenzene and intermediates, the nitro group reduction to the nitroso group is confirmed to be the rate-determining step. The positive slope of Hammett's equation suggests that the critical intermediate in the rate-determining step is in the negative state, which suggests that the active H* should be in polar states (Hδ- and Hδ+). These findings will provide a novel route for the synthesis of substituted anilines and broaden the application of MoSx catalysts under mild conditions.