The conversion of CH4 and CO2 to synthesis gas (H2 + CO) and higher hydrocarbons was investigated over BaTiO3, glass, Ni/SiO2, NiFe/SiO2, and a mixture of Ni/SiO2 and BaTiO3 in dielectric-barrier discharges (DBDs) at low temperatures and ambient pressure. The fresh and spent Ni/SiO2 catalyst samples were characterized by SEM, XRD, BET and TEM. The variation of the permittivity of packing materials with the same size did not influence the reaction significantly. Exposing one metal electrode to plasma could enhance the selectivity to CO in the reaction. The conversion of CO2 and CH4 decreased in the sequence of BaTiO3 > NiFe/SiO2 > Ni/SiO2. A NiFe/SiO2 catalyst increased the selectivity to H2, and both Ni/SiO2 and NiFe/SiO2 catalysts enhanced the selectivity to CO in the reaction. A reaction mechanism of plasma assisted CO2 and CH4 conversion was proposed. Specific input energy (SIE) was an important factor affecting the reaction, and it was possible to alter the product selectivity by optimizing the residence time at a certain SIE over a Ni/SiO2 catalyst.