System and method for transferring encrypted document

PURPOSE: A security file forwarding system and a method thereof are provided to transmit a security document to a general document regardless of filtering of a mail server program by uploading the security file and attaching the security file to URL. CONSTITUTION: If attachment of a security file is requested, the first communication terminal uploads the security file to a mail forwarding control server(200). The first communication terminal inserts URL(Uniform Resource Locator) of the security file transmitted from the mail forwarding control server to a mail body and requests sending to a mail server(300). In case a user of the first communication terminal is an allowed user, the mail forwarding control server stores the security file, generates URL about the security file and transmits the URL to the first communication terminal.