Hydrogen gas concentrations and jet velocities were measured downstream by a high response speed flame ionization detector and PIV (Particle Image Velocimetry) in order to investigate the characteristics of dispersion and ignitability for 40-82 MPa high pressurized hydrogen jet discharged from a nozzle with 0.2 mm diameter. The light emitted from both OH radical and water vapor species yielded from hydrogen combustion, ignited by an electric spark, were recorded by two high speed cameras. From the results, the empirical formula concerning the relationships for time-averaged concentrations, concentration fluctuations and ignition probability were obtained to suggest that they would be independent of hydrogen discharge pressure. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.