The utility model provides a distributed optical fiber leakage monitoring system of an LNG (liquefied natural gas) storage tank, and belongs to the technical field of mechanical vibration measurement, impact measurement and pipeline systems. The distributed optical fiber leakage monitoring system comprises a leakage monitoring system host and on-site distributed optical fiber; the on-site distributed optical fiber is paved in a thermal insulation layer between the inner tank bottom plate and the outer tank bottom plate of the LNG storage tank as well as a thermal insulation layer between the tank walls of the inner tank and the outer tank; and a system host (1), which is arranged far away from the LNG storage tank, is arranged on an optical fiber splice closure (5) outside the top of the LNG storage tank in a connecting manner, and then the optical fiber splice closure (5) is connected with tank wall monitoring optical fiber (3) and tank bottom monitoring optical fiber (4). The technology provided by the utility model is higher in safety control, and can effectively lower environmental pollutions and security risks, caused by leakage of the LNG storage tank.