Method and device for polyphase flowmetry

Multiphase flowmeter method where: * two pressure values P1 and P2 are determined for two different locations A and B, and the value of the internal pressure Po of the device, * the value of the volumetric ratio GLR of the phase is determined gas and the liquid phase of the multiphase medium, and the differential pressures Po-P1 and P2-Po, * from the values determined above, of the knowledge of the specific masses of the gaseous phase and of the liquid phase and / or the average value of the density of the multiphase medium inside a screened tube, a relationship connecting at least the following parameters: GLR, (P1, P2, Po), (rhog, rhol or T 370> m) the total flow rate Qt of the multiphase flow medium and / or the flow rate of each of the phases are determined.