The invention relates to a fiber distributed monitoring system for an undersea tubular pile. The system is characterized by comprising an underwater pressure-proof chamber, a monitoring system body, an optical cable fiber distribution box and an acoustic responder; the monitoring system body is arranged in the underwater pressure-proof chamber and connected with the optical cable fiber distribution box, the optical cable fiber distribution box taps a multi-core optical cable of the monitoring system body into multiple sensing fibers, the sensing fibers are arranged separately on the tubular pile to be measured in the radial direction by penetrating out of the optical cable fiber distribution box, and the monitoring system body monitors and stores state data of the tubular pile to be measured in real time via the sensing fibers; and the monitoring system body is also connected with sea surface equipment and the acoustic responder, the acoustic responder is used for communication betweenthe monitoring system body and the sea surface equipment, and the sea surface equipment provides electric energy and store the state data of the tubular pile to be measured. The fiber distributed monitoring system can be widely applied to the technical field of marine oil gas monitoring.