The invention discloses a big-data-based information steganography method and system and an information extraction method and system. The information steganography method comprises the steps that secret information needing to be subjected to steganography is received; the secrete information is processed and inserted into the position in big data, and information related to the secrete informationin the big data is sent to an authorized person; the information extraction method comprises the steps that the information related to the secrete information in the big data provided by the authorized person is received; the secret information is extracted according to the information related to the secrete information in the big data, and the secret information is sent to the authorized person.Accordingly, on one hand, all users can access the big data publicly; on the other hand, the users can only access the information obtained after the users are authorized, and the big data has both the openness and the safety; due to the fact that the big data is inserted, the steganography capacity of information steganography is greatly expanded in a big data carrier and not limited by the sizeof a traditional carrier, and the capacity of information steganography is greatly increased.