A data storage device includes a flash memory, a controller and a random-access memory. The flash memory includes a plurality of planes, and each plane includes a plurality of blocks. A portion of blocks in each of the planes constitutes a super block, so that the flash memory includes a plurality of super blocks. The controller is coupled to the flash memory. When a first block of at least one first super block of the super blocks is damaged, and a second block of a second super block in the position corresponding to the damaged block is normal, the controller merges the second block of the second super block with the first super block to replace the first block. The random-access memory stores a compression table to record position information about the first block in the first super block and the number information of the second block.