Disclosed are a forensic marking method and a forensic marking system capable of inserting in real-time a forensic mark for user information in digital contents provided online. The forensic marking method of the digital content according to an exemplary embodiment of the present disclosure includes generating a first content created by inserting a first forensic mark in an original content and a second content created by inserting a second forensic mark in the original content by a content server; transmitting the first and second contents to a client terminal by the content server; and combining fragments of the first and second contents in a combination order corresponding to user information to generate a third content by the client terminal