Density functional theory calculations were used to investigate the mechanism of acetylene hydrochlorination separately catalyzed by un-doped B₁₂N₁₂ and carbon-doped BN fullerene (B_12−nN_11+nC (n = 0, 1)). We have discovered that carbon-doped BN clusters displayed extraordinary catalyst performance for acetylene hydrochlorination compared with un-doped B₁₂N₁₂ clusters. C₂H₂ was adsorbed onto B_12−nN_11+nC (n = 0, 1) clusters prior to HCl and then formed three adsorption states. The first two states were in a trans configuration, in which the two H atoms of C₂H₂ were on opposite sides of the CC bond; the third state was a cis configuration, in which the two H atoms were on the same side of the CC bond. Afterwards, we illustrated three possible pathways with corresponding transition states. In particular, the minimum energy pathway R1 based on the B₁₁N₁₂C catalyst had an energy barrier as low as 36.08 kcal mol⁻¹, with only one transition state.