In gas measurement standard device based on sonic nozzle method,negative pressure method and positive pressure method are used to measure fluid models.In order to improve the measurement accuracy and reduce the impact of fluid flow disturbance on the measurement,it is necessary to install a steady flow structure in the front straight pipe section.Current steady flow structure is a combination of pipe,there are still inadequacies.Therefore,the steadyflow structure of the gas flow standard device with sonic nozzle was optimized.The honeycomb combined straight pipe structure was proposed,and two kinds of structure modeling and CFD simulation were completed.By comparing,the honeycomb combined straight pipe shows better results on steady flow.