The invention discloses a multi-protocol information resolving system based on a network packet, comprising gateway equipment 1, a client computer 2, a server 3, a database 4 and an information security server 5, wherein the server 3 is respectively connected with the gateway equipment 1, the client computer 2, the database 4 and the information security server 5; the difference is that the server 3 is provided with a network packet capturing module 31, a protocol analysis module 32, a packet recombination module 33, a mail information reduction module 34, an MSN instant messaging information reduction module 35 and a webpage information reduction module 36. The method reduces to obtain all content of the E-mail, MSN instant communication and HTTP requested key information by the protocol analysis, packet recombination and application layer resolution to the original packet, and two filtering modes of pre-filtering and back filtering are adopted to accurately judge and analyze content filtering.