The purpose of this paper was to investigate the reforming characteristics and optimum operating conditions of the plasmatron-assisted CH4-reforming reaction for the hydrogen-rich gas production. In addition, to increase the hydrogen production and methane conversion rate, parametric screening studies were conducted, in which there were the variations of the CH4 flow ratio, CO2 flow ratio, steam flow ratio, and catalyst addition in the reactor. A high-temperature plasma flame was generated by air and arc discharge. The air flow rate and input electric power were fixed at 5.1 L/min and 6.4 kW, respectively. When the CH4 flow ratio is 38.5%, the production of hydrogen was maximized and the optimal methane conversion rate was 99.2%. Under these optimal conditions, the following syngas concentrations were determined: H-2, 45.4%; CO, 6.9%; CO2, 1.5%; and C2H2, 1.1%. The H-2/CO ratio was 6.6; the hydrogen yield was 78.8%; and reformer thermal efficiency was 63.6%.