This paper presents an experimental application of PID control to study the electrocoagulation process of textile wastewater. The addition of NaCl solution would also lead to the decrease in power consumption because of the increase in conductivity. Conductivity in electrocoagulation process is difficult to control because of the complex nonlinear behaviour involved. Conductivity changes during the textile wastewater treatment and then temperature of the system is changed, as a result some system properties such as viscosity and density have been changed. According to such changes, efficiency of purification change. As a result, control of conductivity for such a system is necessary. Also this study includes a series of tests in which a PID control was used for conductivity control. Due to the non-linear behaviour of the process, the PID parameter adjusting was very difficult but the obtained results showed that PID control with appropriate parameters is suitable for the electrocoagulation process.