Abstract: Investigation results of current neutralization precesses for Intense RelativisticElectron Beam (660kV, 4DkA, 100ns) propagation in neutral gas H_2(13. 3-2. 6)×10~3 Pa are presented in the paper. It is found experimentally that as gas pressureincreases the current neutralization effect varies from weaker to stronger at first andthen weaker again. The minimum ratio of current neutralization is about 15%, as thegas pressure are in about 133. 3 Pa. A numerical simulation of current neutralizationprocesses is made based on the analysis of the gas ionization and charged particlemotion during IREB propagation. The results of the simulation are in goodagreement with the experimental results. Calculation is also made for the temporaland spatial variations of current, electromagnetic fields and charged particledensities in the processes.