Phase change fibers have gained prominence as an advanced functional material for personal thermal management, demonstrating significant potential for practical applications. However, current research systems face critical limitations: conventional phase change fibers prepared via wet spinning and electrospun phase change fiber films suffer from inadequate thermal insulation due to their structural compactness deficiencies, thereby failing to effectively prevent body heat loss in cold environments. To address this technical challenge, this study breaks through traditional material system constraints by innovatively employing electrospinning technology to incorporate polyethylene glycol (PEG) into polyacrylonitrile (PAN) fiber systems. We successfully fabricated fluffy structure phase change fibers that integrate both phase change thermoregulation and thermal insulation functions with the principle of non-solvent-induced phase separation. The internal porous structure of the fluffy fibers constructs an effective cold protection layer, exhibiting an ultra-low thermal conductivity of 0.0395 W/m·K. Simultaneously, the PEG phase change component imparts a high latent heat of 80.6 J/g, achieving a synergistic effect of temperature regulation and thermal insulation. The material demonstrates excellent structural and thermal stability: it maintains stable phase change performance after 500 thermal cycles and exhibits exceptional thermal reliability up to 300 ℃. Even above the phase change melting point, the material effectively prevents leakage of the phase change component. Furthermore, it possesses sufficient mechanical properties to withstand various deformations such as bending, compression (668.7 Pa), and stretching (253.5 kPa) without structural collapse. Practical application evaluations further demonstrate that the material's cold protection performance significantly surpasses that of natural cotton. This study not only provides an innovative strategy for fabricating integrated “heat storage-thermal insulation” fibers but also conceptually expands the design dimensions of phase change fibers in thermal management, offering important solutions and theoretical guidance for developing high performance wearable cold-protection materials.