A high-voltage forming device in which a section of a ferrite-filled coaxial transmission line is used to sharpen the rise time of nanosecond pulses has been studied. It is shown that low-conductivity nickel-zinc ferrites are suitable for sharpening the rise time of submegavolt pulses. Experiments for two versions of the ferrite line and different lengths of the ferrite-filled sections have been performed. The experimental results indicate the possibility of sharpening the rise time of output pulses to 0.7 ns in the range of pulse amplitudes 110–360 kV at a pulse repetition rate of up to 100 Hz.