Abstract: Given wider and wider application of ultra filtration (UF) and reverse osmosis (RO) technology in industrial waste water treatment, it designed a control system with UF and RO based on S7-300 series PLC, and provided real time monitoring for the running status by using Ifix5.0 configuration software as the upper computer. It adopted distributed control structure, and communicated between lower machine and upper computer with using TCP/IP protocol, and collected real-time values through the sensors. This system realized a precise control and real-time monitoring for field devices. The field application shows that this system improves the treatment efficiency of industrial waste water, and has a certain promoting significance to automated production and modern management of enterprises.