The present invention provides a data storage device including a flash memory and a controller. The flash memory includes a plurality of blocks, wherein each of the blocks has a plurality of pages. The controller receives a plurality of write commands in a sequence, assigns a plurality of write sequence numbers to the write commands according to the sequence in which the write commands are received, and writes a plurality of data sectors and the write sequence numbers of the write commands into the pages of a first current block and a second current block of the blocks according to the write commands.