As a potential oxygen evolution reaction (OER) catalyst, Co-based perovskites have received intensive attention. However, Sr readily accumulates on their surface, and makes them inert toward the OER. Herein, we propose a simple but versatile electrochemical reduction method to reconstruct the active surface of Co-based perovskites within a few seconds. By this method, Sr rapidly precipitates from Co-based perovskites, accompanied by the introduction of Sr and oxygen vacancies. After reconstruction, the electrochemical active surface areas of Co-based perovskites greatly increase, and the OER overpotential of the optimized SrNb 0.1 Co 0.7 Fe 0.2 O 3- δ (ER-SNCF-20s) reaches 278 mV at 10 mA cm -2 . This can be explained by the decrease of overpotentials at the rate-determining step. Using ER-SNCF-20s, the splitting voltage of alkaline natural seawater can reach 1.56 V at 10 mA cm -2 , and remains steady for 300 h. This effort offers a feasible method for reconstructing the active surface of Co-based perovskites.