Abstract: A method of a flash memory storage device using a copy back command is provided. An error correction rule is adopted to determine whether or not data errors occurred in the un-amended data stored in the page, wherein when it is determined that data errors has occurred in the un-amended data, then a data transfer command is executed, thereby enabling the flash memory storage device to use the block having a faster transferring speed to executing the copy back command. Thus, the data in the flash memory storage device is not only correct and complete but also the stability of the system is promoted.