The present invention discloses a data access method accomplished by the following steps of: creating a predetermined password; generating a first encryption key; encrypting data based on the first encryption key; prompting for the predetermined password upon receipt of an access request; decoding a header of the NAND flash memory based on a user-entered password; examining the header to determine whether a mapping between the user-entered password and the first encryption key is defined; and decrypting and outputting the data by a decryption key when the mapping between the user-entered password and the first encryption key is defined.