Previous investigations have found that the plasma catalytic conversion of methane is a low-emperature process for the activation of methane, the major component of natural gas. In this paper, the production of acetylene via plasma catalytic conversion of methane over NaY zeolite is discussed. Hydrogen is produced as a by-product during this plasma catalytic methane conversion. A methane/hydrogen feed with oxygen as an additive and helium as a diluent has been studied in this investigation. The CH4/H2/O2 system is found to be more selective for the production of C2 hydrocarbons, compared to the CH4/O2, CH4/H2O, and CH4/CO2 systems reported previously. A higher hydrogen concentration feed is more favorable for acetylene formation. The selectivity and yield of C2 hydrocarbons are related to the hydrogen feed rate, gas temperature, concentration of oxygen additive, and flowrate. The highest yield of C2 hydrocarbons (32%) is obtained at the lowest flowrate used (10 cm3/s; residence time