The sludge dehydration plays a very important role in the modern sewage treatment process. In this paper the process of the sludge dehydration and the design of the control system are introduced, in which the control system consists of process control layer and remote access layer. Process control layer is realized using Siemens S7-1200 PLC and a wireless route is added for remote accessing which utilizes Ethernet and VPN technologies. The functions of the system are described, and the key points of design and implementation methods are presented. The application of this system shows that the cost of sludge treatment is reduced and the reliability of equipment is improved.