For the widespread transmission, custody and utilization for hydrogen energy, accurate flow rate measurement is the precondition. The ultrasonic flowmeter has a prospect of wide application for the hydrogen flow measurement. To improve the measurement accuracy, this article researched the inherent error of the ultrasonic flowmeter in the nonideal hydrogen gas flow. Computational fluid dynamics (CFD) had been used to simulate hydrogen flows downstream of the single right bend and an orifice plate at different Reynolds numbers. Based on the simulation results, this work investigated the inherent error of the ultrasonic flowmeter with different integrations and acoustic paths. The results show the errors become larger when the flowmeter position is closer to the disturbance sources. The increase in the number of acoustic paths can effectively reduce the error caused by the non-ideal flow. In the flow field downstream of the bend, the flowmeters adopting Tailored and Owics integration perform better than those with other integrations. Tchebychev and Owics integration cause less error in the front 4D (four times diameter) pipe downstream of the orifice plate, while Tailored and Owics cause less error in the rear 11D area. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.