A charging method and a related device are provided. A charge protection apparatus includes a micro control unit MCU, a current detection circuit, a gating circuit, and an I/O interface. The current detection circuit detects an external charging current flowing through a power cable. The current detection circuit transmits the external charging current to the MCU. The MCU transmits the external charging current to a user terminal by using the I/O interface, so that the user terminal calculates a current difference between the external charging current and an internal charging current detected by the user terminal, and determines, based on the current difference, whether to generate a circuit control command. The MCU receives the circuit control command sent by the user terminal, and controls, according to the circuit control command, the gating circuit to be in a closed state or an open state.