Abstract: SF₆ gas has a very strong greenhouse effect, the search for new alternative gas to SF₆ has become an urgent case for researchers. This paper studies the discharge characteristics of CF₃I/N₂ gas mixture with needle-plane and sphere-plane electrode under standard lightning impulse, which is important for CF₃I and its mixtures applied in electrical equipment. The results show that the discharge characteristics of CF₃I/N₂ gas mixtures present an significantly polarity effect both in highly non-uniform electric field and slightly non-uniform electric field. When the electrode gap is 5mm, the polarity reversal phenomenon appeared with the increase of gas pressure. The analysis shows that CF₃I/N₂ gas mixture appears polarity effect and polarity reversal phenomenon in the short gap is due to the migration and interaction of space charge between electrode gaps. Electrical equipment using CF₃I/N₂ mixtures as insulation medium should seriously consider about polarity effect and polar reversal phenomenon.