An approach to implementing quadrature double paths OCT and the corresponding signal processing method is presented, meeting the real time processing requirement of electric power transient protection. The current signal can recover directly through the double paths while suppressing the effects of ripples in optical paths. By over sampling in data converting and advanced digital signal processing technique, the response delay to transient failure is lowered down and the detecting performance is improved.The experiment proves this method has lower processing delay and higher precision than the conventional one.