Abstract: The ultrasonic flow meter is a kind of new technology used to measure the How rate ot natural gas. The high precision measurements can be obtained by the digital technology through the mechanism that the velocity of gas flow affects the transmission velocity of ultrasonic in fluid. This technology is characterized by less investment, trusty performance and high accuracy of measurement. This kind of flow meter has not widely applied in gas industry of China. The paper systemically introduces the ultrasonic flow meter in the relative systemic analysis of its principle, characteristics, application scope and dry-type calibration method.