A battery management system for a main system of an electronic device is provided. The battery management system is electrically connected with plural battery units. The battery management system includes plural insertion slots and a battery detachment protection device. The insertion slots electrically connected with the main system. The plural battery units are docked with the corresponding insertion slots. The battery detachment protection device is electrically connected with the main system. When an external force is applied to the battery detachment protection device, the battery detachment protection device generates a system protection sensing signal. In response to the system protection sensing signal, a power supply condition of at least one battery unit in the corresponding insertion slot is adjusted, and the at least one battery unit in the corresponding insertion slot is permitted to be detached from the corresponding insertion slot or positioned in the corresponding insertion slot.