A gas flow metering gas chamber, the gas flow metering gas chamber comprising: a cavity with a gas inlet arranged at one end thereof and a gas outlet arranged at the other end thereof; a first ultrasonic transducer mounting hole being provided at the gas inlet, a second ultrasonic transducer mounting hole being provided at a side wall of the gas outlet, a signal emitting direction of a first ultrasonic transducer installed in the first ultrasonic transducer mounting hole being angled to a direction of the gas flow through the cavity, and a signal emitting direction of a second ultrasonic transducer installed in the second ultrasonic transducer mounting hole intersecting with the direction of the gas flow through the cavity, and a reflection device being provided at the gas outlet, an angle being formed between a reflection surface of the reflection device and the direction of the gas flow, and the reflection surface of the reflection device facing the signal emitting direction of the second ultrasonic transducer installed in the second ultrasonic transducer mounting hole, so that the signals emitted by the first ultrasonic transducer and the signals emitted by the second ultrasonic transducer form a reflection passage through the reflection surface of the reflection device; characterized in that the gas flow metering gas chamber further comprises a fairing mounted in the gas inlet, the fairing comprising a mounting portion located on one end of the fairing and a connecting portion located on the other end of the fairing, the mounting portion and the connecting portion separated from each other to define a diffusion hole therebetween, the fairing further comprising a shielding cover located between the first ultrasonic transducer mounting hole and a plurality of air intake holes, the plurality of air intake holes being defined to surround the first ultrasonic transducer mounting hole, the mounting portion, the shielding cover and the connecting portion, gas diffusely flowing in the fairing from two ends of the fairing, and then flowing in the plurality of air intake holes, the diffusion hole, and the cavity in turn, a direction of the gas being changed when the gas flows from the air intake holes to the diffusion hole, the direction of the gas being changed again when the gas flows from the diffusion hole to the cavity. a cavity with a gas inlet arranged at one end thereof and a gas outlet arranged at the other end thereof; a first ultrasonic transducer mounting hole being provided at the gas inlet, a second ultrasonic transducer mounting hole being provided at a side wall of the gas outlet, a signal emitting direction of a first ultrasonic transducer installed in the first ultrasonic transducer mounting hole being angled to a direction of the gas flow through the cavity, and a signal emitting direction of a second ultrasonic transducer installed in the second ultrasonic transducer mounting hole intersecting with the direction of the gas flow through the cavity, and a reflection device being provided at the gas outlet, an angle being formed between a reflection surface of the reflection device and the direction of the gas flow, and the reflection surface of the reflection device facing the signal emitting direction of the second ultrasonic transducer installed in the second ultrasonic transducer mounting hole, so that the signals emitted by the first ultrasonic transducer and the signals emitted by the second ultrasonic transducer form a reflection passage through the reflection surface of the reflection device; characterized in that the gas flow metering gas chamber further comprises a fairing mounted in the gas inlet, the fairing comprising a mounting portion located on one end of the fairing and a connecting portion located on the other end of the fairing, the mounting portion and the connecting portion separated from each other to define a diffusion hole therebetween, the fairing further comprising a shielding cover located between the first ultrasonic transducer mounting hole and a plurality of air intake holes, the plurality of air intake holes being defined to surround the first ultrasonic transducer mounting hole, the mounting portion, the shielding cover and the connecting portion, gas diffusely flowing in the fairing from two ends of the fairing, and then flowing in the plurality of air intake holes, the diffusion hole, and the cavity in turn, a direction of the gas being changed when the gas flows from the air intake holes to the diffusion hole, the direction of the gas being changed again when the gas flows from the diffusion hole to the cavity.