The invention relates to a moisture liquid phase containing rate measurement device using a dual-ratio method for a three-differential-pressure long throat neck venturi tube; the device comprises a long throat neck venturi tube measurement tube and three differential pressure transmitters: a first differential pressure transmitter, a second differential pressure transmitter and a third differential pressure transmitter; three pressure sampling positions are arranged at an upper reach, a throat middle and lower reach and a lower reach; two pressure outwards drawing pipes connected to the two pressure sampling positions of the upper reach and the throat middle and lower reach are connected to the first differential pressure transmitter; two pressure outwards drawing pipes connected to the two pressure sampling positions of the throat middle and lower reach and an expansion segment outlet lower reach straight tube segment are connected to the second differential pressure transmitter; two pressure outwards drawing pipes connected to the two pressure sampling positions of the upper reach and lower reach of the venturi tube are connected to the third differential pressure transmitter; a front differential pressure, a back differential pressure and a total loss of pressure are obtained by the three differential pressure transmitters respectively. The provided device has a redundancy self-diagnostic function.