Abstract: In the oil-immersed equipment with composite insulation jacket, glass fiber reinforced epoxy resin insulation tube should be used as the main insulation container. The composite insulation tube has long-term contact with the insulating oil, and has been tested under various operating conditions. In order to study the compatibility and long-term stability of insulating pipe and oil, three kinds of insulating pipe materials with different formulations are treated by oil immersion heat aging, and the frequency domain dielectric spectroscopy and gas chromatography related to the compatibility of insulating oil after different aging time are analyzed. The breakdown voltage test, partial discharge characteristic test, surface morphology, frequency domain dielectric spectrum and other anti-thermal oil aging properties of insulating tube materials with different aging time are studied. According to the test results, the thermal oil aging resistance of insulating pipe materials with different aging time is analyzed, and the thermal oil aging resistance and aging resistance of insulating pipe materials with different formulations are compared. The results show that higher shallow trap density is beneficial to charge dissipation, reduce the occurrence of partial discharge and improve the electrical resistance. In addition, the lower degree of epoxy resin decomposition and glass fiber fracture during aging eventually showed good oil compatibility. The results can provide optimal formula and theoretical basis for improving the operation life and reliability of oil immersion equipment with composite insulation jacket.