As an important power grid component, the safety and stability of oil-immersed power transformers are crucial. Under frigid conditions, the kinetic stickiness of insulation oil in the electric equipment shows a tendency to vary significantly, which directly affects the conductivity and polarization characteristics of its internal insulation and exhibits significant differences in performance compared to room temperature conditions. Due to the inevitable need for transformer dielectric property testing during winter handover tests in some areas, it is crucial to research the dielectric properties of oil-paper insulation in extremely cold environments. The existing standard for reducing the insulation resistance of oil-impregnated electric equipment does not take into account the impact of insulation aging, resulting in significant deviations in the reduction results at at frigid conditions. To solve this problem, according to the dielectric response test data and conductivity data acquired under the lab situation for oil-paper insulation in a wide temperature range, incorporating the equivalent scaling calculation model for electric equipment interwinding insulation, this paper considered the insulation aging and presents a normalization comparison method of transformer interwinding insulation resistance in low-temperature environments. The insulation resistance value calculated at low temperatures can be reduced to 20 ℃, which offers a significant theoretical underpinning for accurately evaluating transformer insulation status.