Abstract: Nb3Sn superconductors are vital for advanced applications like particle accelerators and fusion devices, yet their performance degrades irreversibly under the high-strain-rate dynamic loads encountered during quench or fast excitation. This study integrates molecular dynamics simulations, continuum mechanics, and density functional theory to unravel the underlying multiphysics coupling mechanisms. We probe the elastoplastic response, adiabatic heating from plastic work, and damage evolution in Nb3Sn composites under high-strain-rate tension. Our analysis reveals that at cryogenic temperatures, the niobium matrix deforms via full-dislocation slip, whereas the brittle Nb3Sn coating fractures. The associated temperature rise, driven by plastic work dissipation and accumulating with strain, synergizes with deformation-induced damage (amorphization and cracking) to severely degrade superconducting properties. These damage mechanisms cause irreversible electronic structure changes, directly impairing superconductivity. These findings establish a deformation-thermal-damage correlation mechanism, providing a theoretical foundation for the design of resilient superconducting devices.