The performance of reactive oxygen species generator is low in the large-scale application because of the lower operating frequency determined by geometrical scale amplification effect. This paper proposes a method named partitioned operation method whereby the resonance frequency can be kept even if the number of reactor modules increases. The idea is to use n number of low-power high-frequency transformers instead of conventional high-power transformer. One low-power high-frequency transformer and one reactor module constitute a partitioned operation unit, then n number of the partitioned operation units are connected to an inverter, with each unit designed to operate at its optimum operating frequency. The main advantage of the proposed method is to keep the resonance frequency when the number of reactor modules is increased. In addition, the discharge system is very flexible because the number of partitioned operation units can be added or removed as demanded by the ROS generation. In this study, a ROS generator included twenty-four reactor modules was designed and implemented for confirming the feasibility of partitioned operation method. Results show that the efficiency of ROS generation did not decline with the increase of reactor module number.