A multi-passage supersonic gas measuring flow meter of speed-difference method is a novel gas measuring flow meter, relating to the manufacture technology of ultrasonic flow meter. The utility model is suitable for the measuring of common gas flow and pulsating gas with heavy caliber and high volume. The flow meter employs pairs of ultrasonic probes and measures concurrent sound speed and counter current sound speed of the tested gas under the control of a single-sheet machine. A computer converses the flow speed and flow capacity of the tested gas according to the sound speed difference of the tested gas. A ball valve is disposed on a testing tube of a probe tube, realizing exchanging probes at the measuring state. The utility model can not be affected by the change of temperature, pressure, gas composition. Further, the utility model has the advantages of simple structure, convenient testing and high measuring accuracy.