Abstract: In the equipment field with complex service conditions, stringent requirements are imposed on the high temperature resistance and moisture resistance of winding wires. Glass-fiber wrapped winding wires occupy an important position in high-end equipment due to their excellent temperature resistance, yet they have an obvious shortcoming: performance degradation in humid environments, especially a significant decline in insulation performance. This paper focuses on glass-fiber wrapped winding wires and carries out research on their performance degradation under different humid environments. Characterization is conducted by means of scanning electron microscopy, contact angle measurement and other analytical methods to analyze the causes of the decrease in insulation performance, with a focus on exploring the evolution process of the insulation layer interface. The results show that the degradation degree of the insulation performance of the glass-fiber-wrapped winding wire samples after high-temperature aging treatment at 200℃ and 300℃ in a hot and humid environment is significantly higher than that of the unaged samples; the coupled effect of high temperature and humidity will aggravate the accumulation of internal interfacial stress, accelerate the initiation and propagation of surface defects in the resin matrix, promote the continuous penetration of water molecules inward along the defects and interfaces. This causes its insulation performance to decline by 20%-30% at an accelerated rate, ultimately leading to insulation failure. and ultimately lead to the failure of insulation performance.