a boot method for a platform system including a universal extensible firmware interface basic input / output system is provided . the uefi bios includes partitions storing an initial boot program code , a factory setting boot program code , a first customized boot program code , a second customized boot program code and boot information respectively . the provided method comprises steps of : loading the initial boot program code stored in one of the partitions of the uefi bios into a memory , and executing the initial boot program code stored in the memory by a cpu to perform a first phase of boot ; and loading one of the factory setting boot program code , the first customized boot program code and the second customized boot program code stored in the partitions of the uefi bios into the memory according to data in the boot information , and executing the program code loaded in the memory to perform a second phase of boot by the cpu .