The present invention provides a data storage device including a flash memory and a controller. The controller receives a plurality of write commands and a plurality of data sectors from the host. During the period of receiving the data sectors, the controller records that the received data sectors have not been confirmed when the total size of received data sectors has not yet reached a predetermined size, writes a plurality of specific data sectors of the data sectors, which have been received from the host, into the flash memory and transmits a plurality of write-confirm signals corresponding to the specific data sectors to the host when the total size of received data has reached the predetermined size.