SF6 gas is widely used in electrical equipment due to its chemical stability, excellent insulation and arc-quenching properties. However, SF6 has significant greenhouse effects and a high liquefaction temperature, which greatly limits its application. Therefore, finding an alternative to SF6 has become increasingly urgent. In recent years, many scholars at home and abroad have conducted extensive research on this issue. Unfortunately, the various alternative gases studied so far all have drawbacks and are difficult to apply in practice. Therefore, this paper systematically studies the effects of different total pressures and N2/O2 ratios on the insulation characteristics of dry air and N2/O2 mixtures. The results show that dry air at 0.8 MPa and an N2/O2 mixture with 10% oxygen content have sufficiently high insulation strength and could potentially replace SF6.