A hard disk testing method under an extensible firmware interface (EFI) is provided, which includes the following steps. A system file is backed up from the EFI of the hard disk into a storage area of a memory. The backup area of the system file is mapped as a real hard disk. A non-system file storage area is established in the memory, so as to store the non-system files of a hard disk test. Information of the system and non-system files of the hard disk test is acquired, so as to generate a system and a non-system file link table. When performing the test, the non-system files are backed up into the non-system file storage area. The system file link table and/or the non-system file link table is accessed, so as to load the system file and/or the non-system files directly from the storage area of the memory.