The utility model relates to a leakage monitoring system for an underwater natural gas pipeline connector. The leakage monitoring system for the underwater natural gas pipeline connector is characterized by comprising a plurality of underwater sensing subsystems and an overwater monitoring device, wherein each underwater sensing subsystem comprises an external frame, a plurality of hydrophones and an electronic bin are arranged on each external frame, a signal front amplifying plate, a data acquisition plate, a USB data acquisition card and a first optical fiber transceiver are connected into each electronic bin in sequence, the overwater monitoring device comprises an industrial personal computer and a plurality of second optical fiber transceivers connected with the first optical fiber transceivers correspondingly through an optical cable, the industrial personal computer is provided with an operation display interface, and the industrial personal computer displays alarm signals of each hydrophone located at the corresponding position and the leakage position through the operation display interface. The leakage monitoring system can be widely applied to the field of leakage of the underwater natural gas pipeline connectors.