The void fraction and vapor quality are important parameters for characterizing the gas-liquid two-phase flow. However, neither an established void fraction measurement method nor a verified void fraction - vapor quality interconversion model is available for the two-phase hydrogen flow. The object of this study is the development of a void fraction measurement technique and the investigation of the void fraction-quality correlations. A capacitive void fraction sensor was developed using the electric field analysis (EFA) and design of experiment (DOE), and it was applied in a boiling hydrogen experimental facility. The experimental conditions were as follows: the inner diameter of the heating pipe was 15 mm, the mass flux was ranged from 50 to 110 kg/m(2)s, and the static pressure was ranged from 250 to 300 kPaA. Further, the correlation between the thermal equilibrium quality (chi(ac) = - 0.03-0.14) and void fraction (alpha = 0-70%) was compared with that obtained in previously proposed models, and the void fraction - actual quality - thermal equilibrium quality interconversion models applicable to the boiling hydrogen flow were investigated. It was observed that the combination of the Sekoguchi model for thermal equilibrium quality - actual quality conversion and the Steiner drift-flux model for actual quality - void fraction conversion agreed well with the experimental results. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.