Organosilicon-modified polyurethanes (SiPUs) with high‐phenyl‐content and bond energy were synthesized and used as irradiation resistant polymer resins. The mechanical of the SiPU films suggested their feasibility as thermoplastic elastomers with tensile strength above 10.8 MPa and ultimate elongation above 168%. The differential scanning calorimetric (DSC) analysis showed two glass transition temperatures (Tgs, -115°C and 110°C) originating from the organosilicon and polyurethane nanodomains. A two‐step degradation curves corresponding to the organosilicon and polyurethane, respectively, were observed with the temperature of weight loss at 5% (T5%) up to 260°C. By subjecting the SiPUs to different doses of electron beam and γ‐ray irradiation, cross‐linking occurred within the polymers, and the SiPU resins possess excellent radiation resistance, making the SiPU resin as a promising candidate for the radiation resistant applications (e.g., electron beam, γ-ray) and working under extreme conditions with broad service temperature scope (-110 to 110°C).