Phase change fibers, as an advanced functional material for human body thermal management, have significant potential for practical applications. However, current research systems face critical limitations: traditional phase change fibers prepared via wet spinning and electrospun phase change fiber films encounter insufficient thermal insulation due to their structural compactness deficiencies, thereby failing to effectively prevent body heat loss in cold environments. To tackle this technical challenge, this work breaks through traditional material system limitations by innovatively employing electrospinning technology to integrate polyethylene glycol (PEG) into polyacrylonitrile (PAN) fiber systems. We successfully fabricate fluffy-tructured phase change fibers that integrate both phase change thermoregulation and thermal insulation functions using 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. At the same time, the PEG phase change componentprovides a high latent heat of 80.6 J/g, achieving a synergistic effect of temperature regulation and thermal insulation. The material exhibits excellent structural and thermal stability: maintaining stable phase change performance after 500 thermal cycles and exhibiting 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 exceeds 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.