A test bench and simulation model are established to investigate the pressure fluctuations in the port fuel-injected hydrogen system of an internal combustion engine. Analyses are conducted, with injection pressure varied from 0.2 to 0.45 MPa and injection pulse width varied from 2 to 10 ms. The test and simulation results show that more severe fluctuations occur, fluctuation ranges are greater, and decay times are longer under higher injection pressures. Pressure decreases at the curve of pressure at the time during which the injector is opened. This time can be calculated by simulation. to decreases from 1.33 to 0.45 ms at an increase in injection pressure of 0.2-0.45 MPa. Therefore, the hydrogen injection time of the internal combustion engine is accurately controlled by considering to under different conditions. The results serve as guidance in the design of hydrogen rails in hydrogen internal combustion engine. Crown Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.