In order to realize the high efficiency and environmental protection of sludge drying, improve the automation level of sludge treatment process and reduce the intensity of manual operation, a sludge rotary kiln drying control system based on PLC was designed. Combined with the sludge drying process, the control structure composition and procedure of the rotary kiln equipment were designed in detail. In terms of control system hardware, the control scheme with Siemens 200 Smart series PLC as the core was established, and the design of hardware circuit wiring diagram and I/O distribution table was completed. In terms of control system software, in the STEP 7-MicroWIN SMART and WinCC Flexible SMART V3 environments, the manual automatic control program was written and the touch screen interface was developed. Finally, human-computer interaction and full-process automatic control were realized in system simulation and debugging. The results show that the system is stable and reliable, and the drying efficiency is significantly improved, which can dry the sludge with a moisture content of up to 85% to a moisture content of less than 10%, reduce energy consumption and improve the tail gas treatment effect, and meet the needs of industrial production.