This study prepared polyferric sulfate (PFS) coagulants using a closed microwave method. In addition to reducing the requirement of adding oxidant and catalyst by applying the high pressure and high temperatures characteristic of microwave radiation, this work also adopts a newly developed continuous-flow process instead of the conventional batch production method to reduce the reaction time and prevent the energy waste. Water treatment plants can produce coagulants by themselves to meet their requirements since polyferric sulfate is easily created using this microwave method. The transport and storage expenses associated with providing reliable and fresh coagulants for water treatment can thus be reduced or eliminated. The approach specified herein has already been successfully applied to synthesize PFS products and evaluate products' physical and chemical properties, including ORP values, viscosity, salicylic acid reaction ability, and hydrolysis parameter B*. The results reveal that PFS made using the microwave method has properties similar to those of PFS made by the conventional method. Importantly, the microwave method reduces the reaction time from the 500 min of the conventional method to less than 20 min, significantly reducing the amount of energy consumed and the expense of production.