Methods and systems for updating a source image file in a BIOS memory are provided. In one embodiment of the method, an initialization document is loaded to generate a first image file, and the initialization document comprises a function setting and first and second address information associated with the function setting, and the function setting represents whether a system locked pre-installation (SLP) 2.0 is supported. The initialization document is loaded to write an SLP mark and an OEM public key to the first image file according to the first and second address information, serving as a second image file. The second image file is written into the source image file in the BIOS memory.