Abstract: Hydrogen as an important vehicle for global decarbonization goals, the amount of transport is the main bottleneck limiting its large-scale application. Hydrogen blended to natural gas can realize the large-scale ransportation for hydrogen. The hydrogen blended natural gas causes distortion of the flow rate and reduce the performance of ultrasonic flowmeter. In this paper, hydrogen mixed with methane is used as the main working medium. The internal flow field of the 8 types of blended pipelines were simulated and studied. The distribution of gas velocity and hydrogen concentration in the internal flow field were analyzed. The adaptability of the ultrasonic flowmeter is analyzed to determine its recommended installation position. In the adaptability analysis of ultrasonic flowmeter, three-turn spiral pipeline only needs 15D; The adaptability of one-turn spiral tube combined reducer is bigger, the minimum is 96D. By comparison, the blended pipeline C is the best. Hydrogen mole fraction is about 3.9% when hydrogen and natural gas is blended uniformly. The research results can provide reference for accurate metering of hydrogen blended to natural gas with ultrasonic flowmeter.