A data writing method for writing data into a physical block of a rewritable non-volatile memory module is provided. The method includes setting danger distance respectively corresponding to each of the physical pages of the physical block, and setting a secure writing flag in an enable state in response to a secure write command. The method also includes determining whether the secure writing flag is set in the enable state when receiving a write command and updated data thereof; if no, writing the updated data into a predetermined physical page of the physical block; if yes, writing the updated data into a secure physical page of the physical block and re-setting the secure writing flag in a disable state, and the distance between the secure physical page and the predetermined physical page is equal to the danger distance corresponding to the predetermined physical page.