Here we report the first synthesis of nearly pure-phase Cu3Si alloy that can be a highly efficient catalyst in the hydrochlorination of silicon reaction. This material was prepared by a high-temperature (1050 degrees C) calcination method in which copper and silicon powders were used as the reactants. The X-ray photoelectron spectroscopy (XPS) study revealed that the Cu and Si atoms in the Cu3Si alloy carried part of positive and negative charge, respectively. When employed as the catalyst in the silicon hydrochlorination to SiHCl3 (TCS) for the production of Si polycrystals for Solar cell, the sample Cu3Si exhibited excellent low-temperature catalytic performance: the Si conversion and TCS selectivity respectively achieved 41.1% and 96.1% at 250 degrees C. Notably, its TCS yield at 250 degrees C was 1.2 times higher than that of the industrial catalyst-free system at 350 degrees C. Detailed analysis of the reaction process showed that the positively charged Cu atoms and negatively charged Si atoms in Cu3Si alloy could cleave the H-Cl bond in the reactant HCl and make the combination of H and Cl atom with Si atoms easier. Meanwhile, the reaction between the remaining Cu atom and Si was accelerated, leading to the generation of more active Cu6.69Si and ultimately superior catalytic performance. This work deepens the fundamental understanding of the hydrochlorination of silicon reaction, and provides an avenue for the synthesis of Si-based alloy catalysts.