In this paper, a comprehensive study of a DBD reactor is conducted to investigate the optimum operating conditions of the reactor for NOx treatment. For each parameter, the objective is to find the maximum NOx removal efficiency with the minimum consumed power. Different effective parameters of the reactor i.e. electrode length and diameter, electrode and dielectric materials as well as parameters of power generator, i.e. voltage and frequency, are investigated. The results show that for this configuration, the electrode with 20 cm length and 10 mm diameter has the best performance. Aluminum as the inside electrode material and quartz as the dielectric material are selected. Furthermore, the optimum value for the pulse frequency is 16.6 kHz. For the mentioned optimum conditions, the NOx removal efficiency achieved is equal to almost 82% at the input power of 486 W. Furthermore, the highest achieved NOx removal is almost 92% at the input power of 864 W. The results of this paper can be used to reduce the energy consumption of NTP systems to acceptable levels.