A method for enhancing an over-voltage protection by an over-voltage protection device for a generator is provided. The device includes a high voltage excitation off (HEO) circuit lowering an over-voltage level by an over-voltage lockout control value and a voltage-dependent Ki-Kp (VoKiKp) circuit 30 decreasing an over-voltage generation time by a voltage difference value of a battery voltage. A generator setting voltage is provided to operate the over-voltage and the voltage difference value of the generator 1. The over-voltage level is lowered and the over-voltage generation time is minimized, thereby enhancing the over-voltage protection of the regulator of the generator.