Abstract: Introduction With the rapid development of social economy, the underground substation gradually applied in the city 110 kV and above power grid construction, the selection of the transformer which is central to the underground substation. Method In this paper, the characteristics and application of vegetable oil insulated transformer and SF₆ gas insulated transformer were introduced in detail. The advantages and disadvantages of mineral oil insulated transformer, vegetable oil insulated transformer and SF₆ gas transformer were analyzed. Result The results show that SF₆ gas transformer has small land area, good fire resistance, and is suitable for the selection of main transformer of 110 kV underground substation. Conclusion A good design idea for the selection of transformer in underground substation applications is provided as well.