An optical disc drive, comprising an I/O port, coupling to a host to receive a read command that complies with a host terminal file system format; characterized in that further comprises: an optical pickup module, operative to access an optical disc of the optical disc drive, wherein the optical disc contains data recorded in a first file system format that is different from the host terminal file system format; and a format conversion unit, coupled between the I/O port and the optical pickup module, comprising: a mapping information generation module, controlling the optical pickup module to access the data contained in the optical disc, and generating mapping information of the data contained in the optical disc, wherein the mapping information correlates directories recorded in the first file system format to a consecutive directory area of a mapping structure of the host terminal file system format, and correlates all files recorded on the optical disc to an area subsequent to the consecutive directory area, wherein the directories comprise a root directory and at least a subdirectory, wherein the mapping information contains a shift value, the shift value represents an offset between a file access address requested in the read command and a file logical block address; a memory module, storing the mapping information; and a read-command processing module, adding the shift value to the requested file access address to obtain the file logical block address, and controlling the optical pickup module to access the optical disc according to the obtained file logical block address. an optical pickup module, operative to access an optical disc of the optical disc drive, wherein the optical disc contains data recorded in a first file system format that is different from the host terminal file system format; and a format conversion unit, coupled between the I/O port and the optical pickup module, comprising: a mapping information generation module, controlling the optical pickup module to access the data contained in the optical disc, and generating mapping information of the data contained in the optical disc, wherein the mapping information correlates directories recorded in the first file system format to a consecutive directory area of a mapping structure of the host terminal file system format, and correlates all files recorded on the optical disc to an area subsequent to the consecutive directory area, wherein the directories comprise a root directory and at least a subdirectory, wherein the mapping information contains a shift value, the shift value represents an offset between a file access address requested in the read command and a file logical block address; a memory module, storing the mapping information; and a read-command processing module, adding the shift value to the requested file access address to obtain the file logical block address, and controlling the optical pickup module to access the optical disc according to the obtained file logical block address. a mapping information generation module, controlling the optical pickup module to access the data contained in the optical disc, and generating mapping information of the data contained in the optical disc, wherein the mapping information correlates directories recorded in the first file system format to a consecutive directory area of a mapping structure of the host terminal file system format, and correlates all files recorded on the optical disc to an area subsequent to the consecutive directory area, wherein the directories comprise a root directory and at least a subdirectory, wherein the mapping information contains a shift value, the shift value represents an offset between a file access address requested in the read command and a file logical block address; a memory module, storing the mapping information; and a read-command processing module, adding the shift value to the requested file access address to obtain the file logical block address, and controlling the optical pickup module to access the optical disc according to the obtained file logical block address.