Abstract: Traditional naphthenic transformer oils are gradually unable to meet the domestic transformer oil market need, with the rapid development of the power grid. At the same time, the hydroisomerization technology of nonnaphthenic transformer oil is gradually improved and widely used. The research and application of hydroisomerized non-naphthenic transformer oil has received more and more attention. But the application in power transformers of 500 kV and higher voltage level and converter transformers is still in the feasibility study and trial operation stage. The characteristics of dissolved gas and space charge in oil need further research. The related research situation of hydroisomerized non-naphthenic transformer oil was summarized systematically in this paper, including the structural, physical, chemical and electrical properties. Finally, the research and development trends of hydroisomerized non-naphthenic transformer oil were prospected.