New reaction initiation (ignition) system utilizing discharge plasma is proposed for 1N-class reaction control system (RCS) thrusters utilizing green monopropellant; especially for one of hydroxyl ammonium nitrate (HAN) based liquid monopropellants, called SHP163. This reaction initiation system was designed in substitution for conventional catalytic decomposition system. In this study, fundamental reaction initiation characteristics of propellant, based on total amount of energy and propellant mass reduction, were investigated. At the same energy level, higher mass reduction was observed at larger number of discharge attributed from frequency. Additionally, a laboratory model of the reaction initiation system was built, and fundamental characteristics based on power consumption were investigated experimentally. The new reaction initiation system was demonstrated without propellant flow. In order to understand effects of helium mass flow rate and frequency on power consumption and plasma generation characteristics, helium mass flow rate was varied from 3.2 to 27.8 mg/s, while frequency was varied from 100 to 5000 Hz. Power consumption was increased as frequency increased, and the highest power consumption, 34 W, was recorded at 5000 Hz of frequency at 12.9 mg/s of helium mass flow rate. In this study, stable plasma generation was observed at any frequency and helium mass flow rate.