A battery protection device adapted to be electrically connected to a load and a battery set and including a signal terminal, a discharge circuit and a control circuit is provided. The signal terminal is electrically connected to the load. The discharge circuit is electrically connected to the signal terminal. The control circuit detects a sensing voltage from the signal terminal, and counts a number of times that the battery protection device is switched to a protection mode from a normal mode, so as to obtain a counting value. The control circuit determines whether to enter the protection mode or the normal mode according to a reference voltage. In the protection mode, the control circuit adjusts the reference voltage or the control circuit controls the discharge circuit to form a discharge path passing through the signal terminal, the discharge circuit and a ground.