A data storage device is provided. The data storage device, coupled to a host, includes: a flash memory; and a controller, configured to control accessing of the flash memory; wherein when the host performs random data accessing to the flash memory, the controller retrieves address information of a corresponding block and a corresponding page in the flash memory associated with first data to be read based on a global mapping table, and pre-fetches the corresponding page from the flash memory based on the address information; wherein when the controller obtains the address information, the controller further determines whether the first data is located in a current buffer block based on a local mapping table; wherein when the first data is located in the current buffer block, the controller further cancels the pre-fetched corresponding page, and reads the first data from the current buffer block.