Abstract: Using N2 or dry air to replace SF6 as high-voltage switchgear insulation media is a hot topic in the development of environmentally friendly switching equipment. In order to make switchgear equipment with N2 has a much compact structure in space, engineers should fully understand the insulation characteristics of N2. In this paper, the insulation characteristics of N2 with trace water were studied from the point view of electron swarm parameters and the breakdown tests. Firstly, the density-normalized effective ionization coefficient (α-η)/N in N2-H2O gas mixtures were calculated by solving the Boltzmann equation in the condition of steady-state Townsend discharge experiment. Values of the limiting electric field strength for which the electron ionization exactly balances the attachment were derived from the effective ionization coefficient data. Secondly, the breakdown characteristics of N2 with the effect of moisture by the sphere-plate electrodes have been investigated. From the calculation and experiment results, it was revealed that the insulation characteristics of N2 were not severely affected by different water content ranging from 0 μL/L to 1,000 μL/L in N2. And the breakdown voltage was decreased 8~ 15% with increasing moisture contents from 1,500 to 2,000 μL/L.