Abstract: This paper reported an investigation on the effect of thermal oxygen aging on the physical and chemical properties of flameretardant PVC insulation materials (ZR-BVR) used for flexible wire. A critical ambient temperature of 70 ℃ was selected as the aging temperature for ZR-BVR wire, and the aging behavior of the flexible wire was tested and then analyzed by using scanning electron microscope, Fouriertransform infrared spectrometer, microcomputercontrolled electronic universal testing machine and thermogravimetric analyzer. The results indicated that the physical and chemical properties of the aged ZR-BVR were changed during the heat and oxygen aging treatments. Some blisters were observed on the surface of tested specimens, and the absorbance of absorption peak corresponding to the methyl bending vibration decreased when the aging treatment was carried out for 20 days. Some cracks appeared on the surface of test specimens after aging for 40 days. The thermal stability of ZR-BVR decreased gradually, and meanwhile the risk of pyrolysis and combustion seemed to increase gradually. The electrical trees were generated after aging for 60 days. The elongation at break also decreased to 61.78% after aging for 80 days compared to its original value of 244%.