The experiments to study the powerful electric discharge in hydrogen of high density were conducted at the IPE RAS on a two-stage facility. These experiments were performed under the following conditions: stored energy − 140-300 kJ, discharge current − 90-200 kA, charge voltage of capacitive storage − 4.0-6.0 kV. The maximum initial particle density nmax, achieved after the adiabatic compression of gas (just before the discharge), was about 3.3×1022 cm−3. The main electric discharge parameters (arc voltage, arc resistance and current), arc temperature and conductivity and gas pressure were measured and calculated in experiments. Experimental results permit to estimate the sizes of arc channel. The peculiarities of powerful discharges in the hydrogen at the initial conditions close to the state of solid body were defined. The influence of initial concentration of hydrogen particles on characteristics of arc (conductivity and temperature) in the considered range of experiment conditions was estimated.