This work aims to study the kinetics of heterogeneous electro-Fenton (HEF) process used to treat petroleum refinery wastewater by a catalyst made of an activated carbon loaded with iron and cerium. Effects of HEF operating variables such as current density, dose of catalyst, and pH on the removal of COD and reaction rate constant (k_app) were examined. Results showed that decline of COD with time at different operating conditions obeys a pseudo-first-order kinetics with a regression fitting (R²) not less than 0.97. Furthermore, increasing the current density was found to give higher rate of COD removal and k_app to a limit beyond which no longer enhancement can be achieved. Similar behaviour regarding to the dose of catalyst while increasing pH has an adverse effect. The best operating conditions that give high rate of COD removal and k_app were a current density of 10 mA/cm², a dose of catalyst equal to 1.0 g/L, and a pH of 3, in which 86.97% of COD was removed with k_app value equal to 0.0188538 min^-1 which required only13.06 KWh/kg COD as an electrical energy consumption. The present system approved to have high reaction rate and could be applied to treat various types of wastewaters.