The reaction enhancement mechanism of methane steam reforming (MSR) in the nonthermal discharge and catalyst hybrid reaction is presented. Coke deposited on Al2O3-supported Ni catalyst was investigated using temperature-programmed oxidation (TPO) analysis and micro-Raman spectroscopy. Although methane conversion in the hybrid reaction is greater than that of normal catalytic reforming, the normal reaction deposited 5 times more coke than the hybrid reaction. Raman spectroscopy revealed that the superposition of the nonthermal discharge on catalysts produced less graphitized coke compared to the normal catalytic reaction, by which it is easily removed by H2O during steam reforming. Excited species produced by nonthermal discharge are so reactive that their reaction is completed only on the pellet surface: coke formation in the catalyst pore was only slightly detectable. In contrast, large amounts of coke were detected from the surface and catalyst pores in the normal reaction. In the hybrid reaction, CH4 and H2O are primarily excited by electron impact. Therefore, methane dehydrogenation followed by coke oxidation is promoted, resulting in a small amount of coke formation with greater methane conversion than in the normal reaction. The results are well-correlated with Arrhenius plot analysis of the overall forward rate constant for MSR in the hybrid reaction.