A server includes a Southbridge chipset, a USB port, a storage device, a baseboard management controller (BMC), and a switch. When the BMC is powered on and started, the BMC establishes communication between a USB device connected to the server and the BMC by uploading a driver of the USB device from the storage device to memory of the BMC. In response to receiving a firmware update command in relation to the BMC, the BMC disconnects an electrical connection between the USB port and the Southbridge chipset, and establishes an electrical connection between the USB port and the BMC using the switch. Then, the BMC reads updated firmware data from the USB device via the USB port, writes the updated firmware data into the memory, and updates the firmware of the BMC by writing the updated firmware data into the storage device.