The invention provides a liquefied natural gas supplying system and a using method thereof. The liquefied natural gas supplying system comprises a liquefied natural gas tank, a water-bath vaporizer, a water-bath heater and a phase-changing heat-storing device, wherein a gas outlet pipeline is connected with the water-bath vaporizer, the water-bath heater is used for heating gasified natural gas, and a gas outlet of the water-bath heater communicates with the gas outlet pipeline; the phase-changing heat-storing device comprises an electric heater, a phase-changing material layer and a heat-exchanging pipeline, wherein the phase-changing material layer stores heat through the electric heater, and the heat-exchanging pipeline exchanges heat with the phase-changing material layer; and heat-exchanging pipeline communicates with the water-bath vaporizer and the water-bath heater to form a circular pipeline. In the embodiment, heat energy is supplied to the water-bath heater through the phase-changing heat-storing device, and the phase-changing heat-storing device is high in heat storing capacity, high in phase-changing temperature and small in occupied area; and in the natural gas system, phase-changing heat-storing is applied in the gasifying and heating processes at small natural gas sites, daytime and nighttime peak-valley electricity price differentials are utilized to realize nighttime energy-storing and daytime gasifying, and energy consumption can be saved for gasification stations.