The electric performance of the one kind of hydrogenated transformer oil and three kinds of naphthenic transformer oil had been tested by using the experimental methods specified in the GB/T7595-2008. A series of experiments, including dielectric dissipation factor, volume resistivity, dielectric constant, breakdown voltage and electrostatic charging tendency, mechanical impurities, corrosive sulfur and sulfur content had been conducted. Compared with the other three naphthenic transformer oil, the hydrogenated transformer oil performed the best electrical properties.