A method is provided to update firmware of a radio frequency identification (RFID) reader through a network system, wherein a management host issues an update message to a gateway through the network system, and then depending upon the location where reader firmware update data is stored, either the management host transmits the reader firmware update data through the gateway to each designated RFID reader, or the gateway directly transmits the reader firmware update data to each of the designated RFID readers. A microprocessor of the RFID reader stores the received reader firmware update data to a firmware data storage section of a memory unit thereof.