Abstract: A control system, a power supply system, and a method for preventing a floating charge of a battery are disclosed. The control system is applied to the power supply system electronically connected to an electronic equipment and a power supply terminal. The control system includes a current regulator module and a battery management system. The current regulator module includes a switch element and a diode connected in parallel. The battery management system is used for monitoring a capacity of the battery and controlling the switch element; wherein when the capacity of the battery reaches a default value, the battery management system is used for controlling the switch element to stop charging the battery. When the power supply terminal stops providing the power, the battery provides the power through the diode first and then through the switch element to the electronic equipment.