Abstract: Glass fiber reinforced plastic (GFRP) is usually used as an insulating material for superconducting cable terminals due to its excellent insulation properties at low temperatures. However, the inevitable air gap defect in production greatly reduces its insulation life and mechanical properties at low temperatures. This paper studied the degradation mechanism of GFRP materials at low temperatures and explored its influencing factors. By comparing the partial discharge behavior of GFRP at different temperatures, it can be found that low temperature inhibits the partial discharge of GFRP. At the same time, it can be obtained from experiments that the chemical corrosion of material aging products and energy release at low temperatures have little effect on material degradation, and the degradation of mechanical properties and the accumulation of space charges are the main factors for material degradation. Partial discharge at low temperature causes the internal stress concentration of the material, and at the same time, the accumulation of space charge causes the partial discharge energy to be released instantaneously. Based on the degradation of mechanical properties, the internal defects of the material expand and the material deterioration accelerates.