Approaches for updating a Basic Input/Output System (BIOS) program used in a computer system. The computer system includes a central processing unit (CPU) and a non-volatile memory. The non-volatile memory is used to store the BIOS program, and the BIOS program includes a booting area and a program area for storing a first BIOS image file. The update method includes: duplicating a second BIOS image file from an external storage device of the computer system to a designated area of an internal non-volatile storage device of the computer system; changing a flag from a first status to a second status after the duplication is completed; checking the status of the first BIOS image file when the computer system is booted; and booting the computer system by the first BIOS image file or the second BIOS image file according to the status of the first BIOS image file.