Calcium/magnesium acetate (CMA) is known as a low corrosive and environmentally friendly deicer, but is too expensive in comparison to conventional salt deicers. CMA's high cost is mostly attributed to the acetic acid required to produce CMA. This study aimed to develop a hydrothermal reaction system to produce acetic acid from biomass waste. Based on the results obtained using a batch reactor, a continuous flow reaction system with a maximum treatment capacity of 2 kg h(-1) of dry biomass was constructed. Results showed that the highest yield of acetic acid and the conditions for obtaining the highest yield of acetic acid in this continuous flow reaction system were almost the same as those obtained in batch experiments not only for usual wet oxidation but also for the new two-step reaction. Results obtained so far indicate that the continuous flow reaction system developed in this study has the expected fundamental performance to produce acetic acid for both usual wet oxidation and the two-step reaction.