The invention provides a fast information interaction mechanism in a multimedia system and a network transmission method. The fast information interaction mechanism in the multimedia system simplifies protocol format header data size aiming at the simplest data packet enforced by a protocol transmission format, thereby enabling the protocol format to adapt to the fast information interaction; the simplification on the protocol format header data size means to select a reserved field in an original protocol transmission format as a flag bit and provide the selection whether to use the simplified Packet_id, Timestamp, Packet_squence-number three fields, thereby enabling the protocol format header data number of byte to diminish. Furthermore, a fast message interaction format and a two-way fast request response message format are specifically designed, and the designed formats can be used for all media transmission systems. The defect that an efficient two-way fast information interaction mechanism is absent in the existing media transmission system can be solved by use of the fast information interaction mechanism provided by the invention.