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Electrocoagulation was used to treat the high temperature super-heavy oil produced water. The effects of relevant factors were studied, including reaction time, current density and plate distance. The response surface methodology was used to optimize the process conditions. The mechanisms of purification in electrocoagulation and factors affecting electrode passivation were also studied. The results showed that the electrocoagulation could effectively remove oil, COD, and SiO2 from high temperature super-heavy oil produced water. Reaction time had a significant impact on the removal rate of COD and SiO2. When the reaction time was 27.2 min, the current density was 8.6 mA/cm2, and the electrode distance was 1.8 cm, the removal rates of COD and SiO2 were 80.95% and 100% respectively. Electrocoagulation played an important role in the removal of organic matter, which was the multinuclear hydroxy aluminum complex colloid generated by the combination of aluminum ions and OH-. The increase of Cl- in the produced water slightly weakened the passivation of aluminum plates. The increase of SO42- and HCO3- increased the passivation of aluminum plates. When the produced water was neutral, the passivation of aluminum plate was the highest.