The utility model discloses a gas-liquid two-phase fluid identifying device. The gas-liquid two-phase fluid identifying device comprises a data processing module, a sensing unit for detecting gas-liquid two-phase flow, a data transmitting module and a power supply module, wherein the sensing unit and the data transmitting module are electrically connected with the data processing module; the power supply module is electrically connected with the data processing module, the sensing unit and the data transmitting module; the sensing unit is used for transmitting acquired information to the data processing module; the data processing module is used for judging a distribution condition of a gas-liquid two-phase fluid according to the information acquired by the sensing unit. The gas-liquid two-phase fluid identifying device can be used for realizing an automatic monitoring function, is simple to mount and high in reliability. Besides, the utility model further discloses a liquefied natural gas filling system comprising the gas-liquid two-phase fluid identifying device.