In this work, ethylene epoxidation was investigated in a dielectric barrier discharge jet (DBDJ) with a separate ethylene/oxygen feed under oxygen lean conditions. The ethylene (C2H4) stream was directly injected behind the plasma zone in order to reduce all undesired reactions, including C2H4 cracking and further reactions, while the oxygen (O-2) balanced with argon was fed through the plasma zone totally to maximize the formation of active oxygen species. The effects of various operating parameters, such as total feed flow rate, O-2/C2H4 feed molar ratio, applied voltage, input frequency, and C2H4 feed position on the ethylene epoxidation activity, were investigated to determine the optimum operating conditions for this new DBDJ system. The highest ethylene oxide (EO) selectivity (55.2 %) and yield (27.6 %), as well as the lowest power consumption (3.3 x 10(-21) and 6.0 x 10(-21) Ws/molecule C2H4 converted and EO produced, respectively) were obtained at a total feed flow rate of 1,625 cm(3)/min (corresponding to a residence time of 0.022 s), an O-2/C2H4 feed molar ratio of 0.25:1, an applied voltage of 9 kV, an input frequency of 300 Hz, and a C2H4 feed position of 3 mm behind the plasma zone. The superior activity of the ethylene epoxidation in the DBDJ system resulted from a small reaction volume as well as a separate ethylene/oxygen feed.