Abstract: According to the analysis of gas velocity in different sections of a pipeline, the velocity is related to the position of the section. Ultrasonic gas meters measure the cumulative volume by measuring the average velocity of the gas. Flow field disturbance affects the gas velocity distribution in the pipeline and the measurement accuracy. A gas meter is disturbed by two types of flow fields, namely velocity distribution distortion and vortex. This paper proposes a test method for two kinds of flow field disturbance, and focuses on the structure, installation and error algorithm of the disturbance generator. Taking the 1.5 grade G6 diaphragm gas meter as an example, a 0.5 stage sonic nozzle method gas flow standard device was used to test the influence of flow field disturbance under the flow rate of 10 m³ / h. The influence was less than 0.1%. Given the fact that diaphragm gas meters are not affected by flow field disturbance, the feasibility of the method and the accuracy of the algorithm were verified, providing an evaluation method for verifying the adaptability of ultrasonic gas meters to flow field disturbance. It can be used to obtain more complete and accurate test data of ultrasonic gas meters in design and optimization of flow channels, leading to better product quality. The test data of the G6 ultrasonic gas meter showed that it was easily affected by flow field disturbance. The change in the error caused by the disturbance on the inlet side at the flow rate of q_max was 0.30%, greater than the change of 0.11% on the outlet side, and the changes were related to the flow rate. This effect was insignificant at the flow rate of 0.2q_max. In the design of a product, the flow field should be optimized to reduce flow field disturbance.