Abstract: Due to factors such as low gas pressure, large flow rate change and low flow rate, the measurement accuracy of ultrasonic flowmeter is low. In order to solve the above problems, two G2.5 ultrasonic gas meters with two different structures are designed. Through fluid dynamics simulation, the flow field distribution at different flow values of the two pipeline models is obtained. The magnitude and distribution uniformity of the flow velocity field in the area of ultrasonic propagation path are analyzed to determine a more reasonable measuring pipeline. Finally, the related experiments are conducted to verify the validation of the simulation analysis.