Abstract: When HVDC cables operate in freezing areas, the epoxy insulation of cable connectors is usually exposed to extremely low temperatures. To explore the influence of a low-temperature environment on the electrical properties of epoxy resin, epoxy resin samples were treated at −20, −40, and −60 ℃ for 7, 15 and 30 days, respectively. Then, the treated epoxy resin samples were characterized physically, and the DC electrical properties, such as breakdown strength and resistivity, were researched. Moreover, the influence mechanism of the low-temperature environment on the electrical properties of epoxy resin was researched. The results show that the microcracks will gradually appear on the surface of epoxy resin and continue to deteriorate with the increase of the treatment time. The DC breakdown strength and resistivity of epoxy resin show a trend of increasing first and then decreasing. This trend becomes more significant with lower treatment temperatures. However, compared with the sample placed at room temperature for three months without low-temperature treatment, the breakdown strength of the epoxy resin placed at room temperature for three months after low-temperature treatment decreases significantly. This phenomenon is caused by the combined effect of microcrack on the surface of epoxy resin and free volume in it. The improved electrical properties of epoxy resin are mainly caused by the decreased free volume in low-temperature environments. In comparison, the degradation of the electrical properties is caused by microcracks.