A data storage device including a flash memory and a controller. The controller is configured to perform a first error correction on at least one first data sector of a first page of the flash memory when a predetermined condition is satisfied, obtain a data-sector read voltage of the first data sector through the first error correction, retrieve data of a first meta-data sector of the first page by the data-sector read voltage, and perform a second error correction on the retrieved data of the first meta-data sector read by the data-sector read voltage.