NOx　are　main　toxic　by-products　in　the　effluent　gas　when　decomposing　volatile　organic　compounds　in　air　by　a　packed-bed　plasma　reactor.　Several　types　of　materials　such　as　13X　zeolite,　BaTiO3　and　Pd/Pt　catalysts　have　been　selected　to　be　packed　in　the　reactor,　and　methane　decomposition　and　NOx　by-products　in　discharged　gases　are　investigated　at　different　range　of　reaction　temperature　and　discharge　energy　density　at　atmospheric　pressure.　The　ratios　of　methane　decomposition　percentage/NOx　concentration　are　used　to　assess　these　packed　bed　materials　and　reaction　conditions.　The　results　show　that　using　Pd/gamma-Al2O3　with　lower　percentage　Pd　as　packed　bed,　and　discharging　with　lower　discharge　density　at　higher　reaction　temperature　can　reduce　NOx　output　effectively　and　greatly　improve　performance　of　the　reactor.