[en] The superconducting RF (SCRF) cavities require a very high quality interior surface finish without any defects or impurities for good performance. Electro-polishing is generally preferred as the surface processing method to produce reproducible performance for cavities. A horizontal electro-polishing facility is developed to polish single and multi-cell 650 MHz SCRF cavities. Electro-polishing (EP) procedure for SCRF cavities is very complex, involving handling of large quantity of toxic electrolyte (solution of hydrofluoric and sulphuric acid), arrangement to rotate the cavity, supplying current to moving cavity, changing cavity position during polishing and rinsing, data acquisition and control of various operating parameter, etc. A PLC based control system is developed to monitor and control circulation of acid and water and monitor various parameters like voltage, current, temperature etc. during electro polishing process. Pneumatically operated pumps and valves are used to circulate acid / water. PLC is used to incorporate various interlock while operating solenoid valves. A GUI is developed using LabVIEW to monitor and control the process. The cavity is rotated during EP. The temperature at various locations on cavity is measured using thermocouples and a wi-fi based temperature transmitter. The paper discuss the details of the control system for electropolishing setup at RRCAT. (author)