Disclosed herein is a digital radiography system which provides detachable and portable flat panel detectors (hereinafter, referred to as ‘electronic cassettes’) and transreceives data recorded in the electronic cassettes in on-line through a network. The digital radiography system includes bucky trays on which a plurality of portable electronic cassettes is detachably mounted, and a workstation connected with the bucky trays through communication to identify the plurality of portable electronic cassettes mounted on the bucky trays and to download pre-processing files of the identified electronic cassettes through the network or a portable storage device or to store files, generated by the plurality of electronic cassettes, in the storage device.