An alarm-including protection apparatus and method thereof are used to protect a lithium-ion battery with a plurality of series cells. The protection apparatus includes a voltage balance controller for detecting the terminal voltage of each cell and correcting the terminal voltage of each cell. A protection unit and the lithium-ion battery are connected in series. A microprocessor connects to the voltage balance controller and the protection unit for receiving the terminal voltage of each cell and figuring out a voltage difference between the maximum terminal voltage and the minimum terminal voltage of the series cells. According to the comparison result of the voltage difference and a plurality of critical voltage differences, the microprocessor is used to correct the terminal voltage of each cell, generate an alarm signal or stop charging to the lithium-ion battery.