This is a fundamental study on a design of a plasma reactor and its electrical and hydrodynamic properties. In this study, the electrode structure suitable for this method and its installation position in the reactor were examined. The structure uses a ceramic tube and a stainless steel rod, making it possible to use high conductivity water. The pressure inside the reactor was measured, and the electrode was placed at a position where cavitation was minimum. Then, the cavitation was observed in a sample of water with a conductivity of about 10 mS m−1, and the plasma was also observed. It was found that about 20% of the total power input between the electrodes was used for plasma generation. The hydrogen peroxide concentration proportional to the input power was observed, and a concentration of about 5.5 mg l−1 was obtained at an input power of 20 W when the volume of water was 1.8 l. And also the energy yield of H2O2 generation was 5.9 g kWh−1.