A radio-frequency (RF) plasma system was used to convert methane gas. The reactants and final products were analyzed by using an FTIR (Fourier transform infrared spectrometer). The effects of plasma operational parameters, including feeding concentration (C) of CH4, operational pressure (P) in the RF plasma reactor, total gas flow rate (Q) and input power wattage (W) for CH4 decomposition were evaluated. The results showed that the CH4 decomposition fraction increases with increasing power input, decreasing operational pressure in the RF plasma reactor, decreasing CH4 feeding concentration, and decreasing total gas flow rate. In addition, mathematical models based on the obtained experimental data were developed and tested by means of sensitivity analysis.