In order to study the modification mechanism of Lanthanum doping on SnO₂ catalytic electrodethe. In this paper, La doped Ti/Sb-SnO₂ electrode was prepared by sol-gel method. Taking phenol as a target organics, the electrochemical performance of the electrode was investigated. Polarization curves and Mott-Schottky curve of the prepared electrodes were tested, the analysis results showed that the oxygen evolution potential of lanthanum modified Ti/Sb-SnO₂ electrode is first increased and then decreased. And the exchange current density of Sn:Sb:La 100:10:1.5 electrode is maximum under 2.0V potential. The La doping promotes the negative shift of flat band potential and the slope of fitting straight-line of Mott-Schottky curve has fallen from 2.96 to 1.66, enhances the active surface area, improve carrier concentration correspondingly. Cyclic voltammetry and electrochemical impedance spectroscopy of prepared electrodes were performed, the results showed that the electrochemical reaction resistance of the doped electrode is decreased, the active charge can be increased from 14.1μF to 322μF. At the same time, the peak current of the direct oxidation of phenol is enhanced, the peak potential is decreased. The above results explain the intrinsic reason for the improvement of the electrocatalytic activity.