This paper is devoted to experimental investigation of dependence of flashover plasma parameters: pulse amplitude, current and duration. Two types of generators were used. 1) The pulse cable generator with pulse durations of 5, 35, 50 and 100 ns. 2) RADAN generator with 150 kV pulse amplitude and 5 ns duration. High-pressure polyethylene was used as dielectric. The discharge electrodes were made of copper. Two types of electrode arrangement were used: 1 - coaxial, 2 - linear. Anode - cathode gap was 1 mm - 50 µm for cable generator and 1 cm for RADAN generator. The results of experiments show, that there is no considerable dependence of ion energy and mass-charge composition of a pulse amplitude, electrode arrangement and interelectrode gap. Total ion charge generated by flashover discharge depends on discharge time and area of dielectric surface that discharge occurs on. There is straight dependence of ion energy to an ion charge. Time of ion charge composition formation establishing is about 5 ns.