Investigations of the magnetic field influence on energy (power) released in discharge, the electronic temperature, particle concentration, and the radiation of plasma of the channel-arc stages has a practical focus. It was found that the magnetic field leads to an increase in current density, conductivity, and specific energy input and a decrease in the formation times of all stages of discharge development, transverse integral radiation, and channel expansion rate, and shifts in the maximum spectral density of radiation in the ultraviolet region with simultaneous generation of new spectral lines. The magnetic field decreases the rate of spark channel expansion and the loss of transverse radiation and increases the specific power, conductivity and temperature of the plasma at channel-arc stages, creating conditions for obtaining a hot plasma.