The purpose of this paper is to investigate the characteristics and optimum operating conditions of the plasmatron-assisted CH4 reforming reaction for the hydrogen-rich gas production. In order to increase the hydrogen production and the methane conversion rate, parametric screening study was conducted at various CH4 flow ratio and steam flow ratio and with and without adding catalyst in the reactor. High-temperature plasma flame was made with air and arc discharge, and the air flow rate and the input power were set to 5.1 L/min and 6.4kW, respectively. When the steam flow ratio was 30.2%, the hydrogen production was maximized and the optimal methane conversion rate was 99.7%. Under these optimal conditions, the following syngas concentrations were determined: H-2, 50.4%; CO2 5.7%; CO2, 13.8%; and C2H2 1.1%. H-2/CO ratio was 9.7 and the hydrogen yield was 93.7%. (C) 2007 Elsevier Ltd. All rights reserved.