The invention discloses a gas flow rate measuring device, which comprises a hard tube, a flexible tube, sealing and clamping sleeves and a gas pressure sensor, wherein the hard tube sleeves the flexible tube, the number of the sealing and clamping sleeves is two, the sealing and clamping sleeves are arranged at two ends of the hard tube, a gas pressure cavity is formed among the hard tube, the flexible tube and the sealing and clamping sleeves, and the hard tube and the flexible tube are not in contact with each other; and the gas pressure sensor comprises a probe, the gas pressure sensor is arranged outside the hard tube, and the probe of the gas pressure sensor passes through the tube wall of the hard tube and is arranged inside the gas pressure cavity for detecting gas pressure magnitude in the gas pressure cavity. The gas flow rate measuring device measures a flow rate of a gas flowing through the interior of the flexible tube indirectly through measuring the gas pressure magnitude in the gas pressure cavity, thus cannot affect the gas flow rate inside the flexible tube; and the probe of the gas pressure sensor is arranged outside the gas pressure cavity, and the flow rate of the gas flowing through the interior of the flexible tube does not affect the probe, thereby being capable of reducing measurement errors.