There is a demand for specialized clothing for high-altitude areas to combat extreme cold conditions, icy winds, etc. These clothing should be lightweight, breathable, durable, and provide sufficient thermal insulation. In the current work, we have attempted to develop a polyurethane/silk blend to achieve highly efficient, biocompatible, high thermal insulation, de-icing, and waterproofing capabilities. Utilizing a polyurethane/silk blend maximizes the environmental friendliness of polyurethane and the natural attributes of silk, resulting in a versatile and high-performing textile for diverse applications, especially in advanced clothing systems. PU fibers exhibit flexibility and elasticity at lower temperature due to their low (Tg) and low thermal conductivity. Simultaneously, silk contributes high heat retention, increased thermal conductivity, and effective moisture absorption, making it an ideal fabric for clothing. Polyurethane was synthesized through a two-step solvent method: initially forming a prepolymer and then extending the chain using a chain extender(Bis (2 hydroxyethyl disulfide). It offers a distinct advantage as the bond length of S-S is longer than that of C-C, which lowers the ability barrier for molecular chain rotation. Following this, a blend was prepared using the solution blending method. After blending, fiber was synthesized using the wet spinning method, in an in-house built setup. A variety of analytical techniques were to study the characterization of PU/Silk composite fiber. DSC was used to study the glass transition temperature (Tg) and thermal behavior, FTIR was used to identify chemical bonds and functional groups, NMR was used to identify chain extender links, TGA was used to examine material decomposition analysis, SEM was utilized for evaluating fiber morphology and GPC is used to measure molecular weight. Furthermore, the temperature conductivity was evaluated using LFA. It was found that the synthesized PU/silk fibers were flexible at low temperature, with good thermal insulation and de-icing properties. Apart from high-altitude clothing, these fibers can be used for parachute fabric, sports clothing, etc.