A processing system and a method for updating firmware online, the processing system executes following steps of: an electronic device sending a download request to a firmware security update server end; the firmware security update server end searching for a new version firmware information; if having the new version firmware information, the firmware security update server end decrypting an encrypted new version firmware file into a new version firmware file, and encrypting the new version firmware file with a unique feature to generate an exclusive encrypted new version firmware file, and generating a load point path information; and the electronic device receiving the load point path information, linking to the firmware security update server end and downloading the exclusive encrypted new version firmware file, and the electronic device decrypting the exclusive encrypted new version firmware file with the unique feature to obtain the new version firmware file.