Glass fiber reinforced polymer (GFRP) has been widely used in the production of insulation pull rods because of its light weight, high strength, excellent insulation properties and corrosion resistance. Because of the complex operation condition of the insulation pull rod, the electrical property is the key point to ensure its reliable operation. Herein three types of samples with different fiber orientations were prepared by vacuum casting equipment. By applying AC voltage to different types of samples, electrical tree deterioration experiments were carried out, and the development process of electrical tree in 20 minutes was recorded. The results show that compared with the epoxy resin sample, the electrical tree in the GFRP sample is easier to grow along the direction of the fiber, and the growth rate is increased. Comparing the samples with different fiber orientations, it is found that the sample with an angle of 45 degrees with the needle electrode has relatively superior tree propagation resistance performance, which is similar to the epoxy sample.