The present invention provides a data storage device including a flash memory and a controller. The flash memory has a plurality of blocks, and the blocks include a current block and temporary block. The controller writes a first data sector corresponding to a first logical address into the current block, and determines whether the temporary block has a second data sector that also corresponds to the first logical address, wherein when the temporary block already has a second data sector corresponding to the first logical address, the controller writes a first temporary-block table into the temporary block.