For the continuous operation of emulsion Polymerization of styrene using ultrasound, the system structure for indirect ultrasonic irradiation was investigated. From examination of the structure of flow reactor that could utilize ultrasound field, it was found to be necessary for the reactor design to consider the configuration of the bottom facing the transducer, the method for supply of nitrogen gas, and the liquid level inside the reactor. Consequently, application of a perpendicular cylindrical reactor was proposed, which was effective for the indirect irradiation system. Next, the dynamic behavior of a continuous polymerization system employing the above-mentioned reactor model was analyzed. It Was found that the flow operation based on an appropriate mean residence time resulted in lower polydispersity of the product than the batch operation. Moreover, it was demonstrated that application of a recycling system and modification of the system structure could intensify the process using ultrasonic irradiation.