In this work, first principle DFT calculations are carried out to identify the active center and reveal the reaction pathway on nitrogen and boron doped carbon catalysts in acetylene hydrochlorination. Various different dopant configurations including pyridine, graphitic, and pyrrolic are explored and compared. The different geometries of dopants give the distinct electronic structure, which indicate that pyridine configuration with three dopants around a vacancy, have more states around Fermi level. The adsorption of acetylene (C2H2) is predicted to be the first step of the reaction as it has much bigger binding energy than another reactant, HCl. Boron and nitrogen doping exhibit opposite effect on the charge transfer between adsorbed C2H2 and the catalyst. The curvature of tube also influences acetylene adsorption and the binding energy decreases with increasing tube diameter. Moreover, the detailed reaction pathway is revealed from the calculations. A balanced activity for C2H2 adsorption and HCl activation is required to improve catalytic performance and too strong binding of C2H2 hinders the followed steps on the pathway and cause large barrier. This work clarify the confusions facing by the metal-free doped carbon catalyst and lay out solid base for the future improvements in acetylene hydrochlorination.