A data storage device is coupled to a host, and comprises a flash memory and a controller. The flash memory comprises a spare block pool and a data block pool, wherein the spare block pool comprises a plurality of spare blocks, and the data block pool comprises a plurality of data blocks, wherein a hot spare block count indicates a total number of the hot spare blocks. The controller receives target data from the host, writes the target data to a current data block, determines whether a current programming page is a first page of the current data block, determines whether the hot spare block count is greater than zero when the current programming page is the first page, and sets data move information for a wear-leveling process when the hot spare block count is greater than zero.