A computer system with a damaged BIOS data recovering function is disclosed. When BIOS data in the computer are damaged, the computer system may update and recover the BIOS of the storage unit of the computer system in a standby mode via an external electronic device (another computer or a USB flash disk). The computer system includes a storage unit, a data transferring interface, a power supply unit, and a control unit. The computer system is electrically connected with the external electronic device via the data transferring interface. The power supply unit provides standby power (in the standby mode) when the computer system is shut down. The control unit is electrically connected with the power supply unit and the data transferring interface, respectively. The control unit is actuated via the standby power, receives the external BIOS stored in the external electronic device.