A method for determining a type of a disk and an optical storage apparatus thereof are provided. The method includes when the disk placed in the optical storage device is not a blank disk, determining whether the phases between a first signal and a second signal of the disk are the same or not; and determining that the disk is a low to high (LTH) data disk or a high to low data disk (HTL) data disk upon whether the phases of the first signal and the second signal are the same or not. Therefore, the reading parameters are correspondingly loaded in the optical storage device according to the type of the disk.