Fiber reinforced epoxy resin has the advantages of high strength, corrosion resistance, good insulation performance and light weight, and has been widely used in the production of insulation pull rod. Due to the complexity of the working environment of insulation pull rod, different fiber materials are usually used to enhance certain properties of epoxy resins. In this paper, electrical tree degradation experiments were carried out on glass fiber reinforced epoxy resin and polyester fiber reinforced epoxy resin under tensile stress. The needle electrode is close to the fiber cloth and is parallel to the cloth surface, the direction of the applied tension is parallel to the direction of the electric field, and the tension varies between 0 and 30 MPa. The results show that the electrical tree in glass fiber reinforced epoxy resin (GREP) is more dispersed than those in polyester fiber reinforced epoxy resin (PREP) under the condition of no applied stress. Under tensile stress, the electrical tree in both materials undergoes obvious morphological changes, and PREP is more significantly affected by stress.