A device for a mobile terminal for identifying whether an external power supply device in form of a charger or in form of a computer is plugged into the mobile terminal, characterized in that the device comprises: - a USB interface module connectable with the external power supply device, - an interface detection and control module, - an electronic switch module, - a charging switch module, - an identification module, and - a baseband USB data transceiving module; - said interface detection and control module is connected with said USB interface module and is configured to detect when the external power supply device is plugged into said USB interface module in which case the interface detection and control module is configured to initialize and output a first control signal to said electronic switch module, the interface detection and control module is further configured to detect D-port signal of said USB interface module, and to generate an interrupt response when a level of D- port signal is pulled to the same level as D+ port signal of said USB interface module so as to output a second control signal to said electronic switch module; - said electronic switch module is connected with said USB interface module and configured to receive input signals from said USB interface module, and to select said input signals according to said first and second control signals to connect with said baseband USB data transceiving module and to enter a USB mode when receiving the first control signal or with said charging switch module and to enter a charger working mode when receiving the second control signal; - said charging switch module is connected with said electronic switch module and is configured to switch and output an identification signal according to an output signal of said electronic switch module; - said identification module is connected with said USB interface module and charging switch module, respectively, and is configured to identify the type of said external power supply device that is plugged into the mobile terminal according to signal states of said USB interface module and charging switch module, so that if the output state of the charging switch module changes, the currently plugged power supply device is a charger; otherwise, the currently plugged power supply device is a computer's USB A series interface. - a USB interface module connectable with the external power supply device, - an interface detection and control module, - an electronic switch module, - a charging switch module, - an identification module, and - a baseband USB data transceiving module; - said interface detection and control module is connected with said USB interface module and is configured to detect when the external power supply device is plugged into said USB interface module in which case the interface detection and control module is configured to initialize and output a first control signal to said electronic switch module, the interface detection and control module is further configured to detect D-port signal of said USB interface module, and to generate an interrupt response when a level of D- port signal is pulled to the same level as D+ port signal of said USB interface module so as to output a second control signal to said electronic switch module; - said electronic switch module is connected with said USB interface module and configured to receive input signals from said USB interface module, and to select said input signals according to said first and second control signals to connect with said baseband USB data transceiving module and to enter a USB mode when receiving the first control signal or with said charging switch module and to enter a charger working mode when receiving the second control signal; - said charging switch module is connected with said electronic switch module and is configured to switch and output an identification signal according to an output signal of said electronic switch module; - said identification module is connected with said USB interface module and charging switch module, respectively, and is configured to identify the type of said external power supply device that is plugged into the mobile terminal according to signal states of said USB interface module and charging switch module, so that if the output state of the charging switch module changes, the currently plugged power supply device is a charger; otherwise, the currently plugged power supply device is a computer's USB A series interface.