In this work, S doped Fe2B (Fe2B-S) was synthesized by sintering method and applied for the enhanced dechlorination of trichlorethylene (TCE). The degradation ratio (D) of TCE was 99.8% with reaction rate constant (kobs) of 0.956 h-1 by 10.0at% S doped Fe2B (corresponding to Fe2B-S10.0), compared to D and kobs values 37.3% and 0.067 h-1 by Fe2B, respectively. The major dechlorination products of acetylene, ethene, ethane and C3-C6 hydrocarbon compounds were observed from a reductive beta-elimination pathway. S doped and undoped Fe2B could form the first-level in-situ galvanic cell, and the returned S provided a second-level galvanic cell to further enhance electron transfer. The doped S worked as electron donor to increase the density of localized unpaired electrons, and the electron enriched Fe atoms leading to stronger reducibility were verified by the density functional theory (DFT) calculation. This work provides a complete insight into the enhancement mechanism of S doped Fe2B and guides the potential design of zero-valent iron (ZVI) with properties tailored for chlorinated hydrocarbons dechlorination.