The two electrochemical synthesis of N₂0₅ by oxidation of N₂O₄ and by dehydration of HNO_３ are reviewed, and the comparison between these two methods is given by analyzing the current efficiency, the specific energy, the current density and the chemical yield of the electrolytic process. The importance of cell membrane and the electrode affecting the current efficiency and the specific energy of the electrolysis are presented, and the evaluations of the cell membranes and the electrode materials suitable for the electrolytic system are given. The development and prospect on the research of N₂O₅ are proposed either.