In order to improve the capacity of polyferric sulfate，stable the product quality，reduce the raw material consumption，guarantee production safety，minimize the impact to the environment，Programmable Logic Controller（PLC） intelligent control system was implemented on the basic of the original processes，such as reaction kettle stirring heating production process and circulating pump and ejector production process.The process and technical control point were refreshed and improved.Result showed：by introducing PLC，the unit consumption of liquid oxygen was decreased from 0.025 t/t to 0.019 t/t and sodium nitrite was reduced from 0.01 t/t to 0.005 t/t.Furthermore，the variance of total iron content decreased from 0.02 to 0.003，and variance of basicity decreased from 0.883 to 0.529. It basically realized the target of zero emission of nitrogen oxide and ensuring process stability was realized.The greatest guarantee of safety and environmental protection was achieved.