The effect of adding hydrogen to a nitrogen dc glow discharge is investigated by using Monte Carlo code to simulate the electron behavior in the cathode dark space (CDS). It is shown that when increasing the percentage of H2, the electron mean energy is increased, the electron density and various e-N2 collision rates are decreased, and when adding small amounts of H2 into nitrogen gas, e-N2 dissociation and electron excitation rates can be enhanced under certain discharge conditions, which will contribute to increase the density of significant active nitrogen species (N*2，N+，N) in discharge space. The hydrogen concentration is varied between 0% and 30%. These effects can be explained by the collisions taking place in the discharge. We have also compared our calculated results with experimental data.