A data storage device includes a memory device and a memory controller. The memory controller selects a predetermined memory block to receive data and records multiple logical addresses in a first mapping table. The first mapping table records which logical page the data stored in each physical page of the predetermined memory block is directed to. A bit table is stored in a buffer memory and includes multiple fields. Each field records a bit value. When the memory controller writes data of a logical page that corresponds to a first logical address into the predetermined memory block, the memory controller records the first logical address in the first mapping table, converts the first logical address according to a predetermined function to generate a first field index of the bit table and sets the bit value corresponding to the first field index as a first value in the bit table.