Provided is a data loss prevention system comprising an address converting module for converting a private IP address of a received traffic into an IPv6 address; a first communication module for decoding the received traffic; the data loss analyzing module for analyzing the traffic transmitted from the first communication module according to a predetermined policy and examining whether personal information or confidential information is included; and a second communication module for transmitting the traffic transmitted from the data loss analyzing module to the address converting module after the traffic is encoded or not encoded according to the information representing whether the traffic is encoded included in the IPv6 address, wherein the address converting module restores the IPv6 address of the traffic transmitted from the second communication module to the private IP address.