The invention belongs to technical field of gas-liquid two-phase flow measurement of wet gas and relates to a double differential pressure moisture flow measuring device based on a long-throat-neck venturi. The double differential pressure moisture flow measuring device comprises a venturi measuring pipeline, a first differential pressure transmitter and a second differential pressure transmitter. A pressure taking position is respectively arranged at the upstream of the venturi measuring pipeline and the mid downstream and the downstream position of the throat, four inner pressure taking holes are arranged on the pipe wall of an identical plane perpendicular to the axis of each pressure taking position, and an annular chamber structure is fixed on the periphery of the four inner pressure taking holes. The first differential pressure transmitter is respectively connected with an external pressure introduction pipe connected with the two pressure taking positions at the upstream and the mid downstream of the throat, and the second differential pressure transmitter is respectively connected with an external pressure introduction pipe connected with the pressure taking position at the mid downstream of the throat and the pressure taking position at the downstream. The measuring device has the advantages of being simple in structure, free of movable parts, reliable in measurement, high in accuracy and simple and convenient to implement.