Abstract: Mesh MMO was used as the anode material in the cathodic protection project of the outside floor of the oil tank,and the high purity Zinc and Cu/CuSO₄ were used as reference electrodes to monitor cahtodic protection results. From the results of 5 years,more than 95% of cathodic protection potentials of the outside floors were more negative than -0.85V(vs. CSE),so the outside floors of the oil tank were in good cathodic protection.