The invention discloses an on-sea intermediate frequency digital broadcasting system, comprising: an information management sub-system used to collect and control various kinds of on-sea security information, to create the information files requiring to be transmitted, and to create the emission sequence according to the priorities and the repetitive requirement of the files; an offshore broadcasting and transmitting station to receive and convert the information files from the information management sub-system into an OFDM signal and broadcasting the RF signal to a ship through antenna radiations; and a ship mounted receiver to receive wireless electric signals, to modulate the OFDM signal, to re-create the information files, and according to the application classification of the information files, to display the information contents or provide the information files to a designated device. The information management sub-system and the offshore broadcasting and transmitting station are connected through an offshore network; the offshore broadcasting and transmitting station is connected with the ship mounted receiver through a wireless transmission channel. The on-sea intermediate frequency digital broadcasting system proposed by the invention is able to make the ship information system and the device connected in a seamless manner; and therefore, the broadcasting and transmitting efficiency is high; the coverage is wide and the requirement for broadcasting and transmitting various kinds of MSI data can be fulfilled.