An innovative method was used to simulate ethylene oxide (EO) oxidation in an RF plasma reactor. The objective of this work was to simulate the stable species mole fraction profiles measured in a flowing plasma system at constant temperature and pressure. The mechanism involved participation of 36 species in 140 elementary reactions. Sensitivity analysis was also performed to identify the order of significance of reactions in the mechanism of the model’s predictions. The results show that the main reactions for EO decomposition changed with a varying O2/EO ratio in the plasma system. That is to say, the most important reaction to the O2/EO ratio of zero was the electron dissociation reaction of EO, C2H4O + e- → CH3CHO + e-. While, the most influential reaction for EO decomposition at O2/EO ratio of 5.0 was the formation reaction of HO2, which forms OH radicals, then enhances the decomposition of C2H4O by the reaction, C2H4O + OH = C2H3O + H2O.