The invention discloses a cable type submarine earthquake monitoring system which comprises a main subsystem and a plurality of secondary extended subsystems, wherein the main subsystem is formed by connecting two earthquake monitoring shore base stations on a shore with a plurality of primary submarine earthquake monitoring stations in series, and forms an energy and data aggregation connection network of the submarine earthquake monitoring system; each secondary extended subsystem consists of a primary submarine earthquake monitoring station and a plurality of secondary submarine earthquakemonitoring stations cascaded layer by layer; each primary submarine earthquake monitoring station is used for realizing acquisition of earthquake data, carrying out digital processing on the collecteddata, receiving data sent by the secondary submarine earthquake monitoring stations connected with the primary submarine earthquake monitoring station, summarizing all the data and sending the data to the earthquake monitoring shore base stations; and each secondary submarine earthquake monitoring station is used for realizing acquisition of the earthquake data, carrying out digital processing onthe collected data, receiving the data sent by other secondary submarine earthquake monitoring station connected with the secondary submarine earthquake monitoring station, summarizing all the data and sending the data to the previous submarine earthquake monitoring station through an extended submarine cable.