Targeted protein degradation via PROTACs holds promise for antiviral therapy but is challenged by inefficient ternary complex formation. We report the de novo design of PROTACs targeting the SARS-CoV-2 RNA-dependent RNA polymerase (RdRp). Leveraging repurposed antiviral scaffolds and optimizing E3 ligase ligands, we designed and screened 600 candidates. Our integrated pipeline identified PROTAC 10, a molnupiravir-CRBN conjugate, which demonstrated high-affinity binding (Kd = 1.09 nM), pronounced positive cooperativity (α = 45.9), and effective CRBN-mediated RdRp degradation (DC50 = 1.97 μM) in infected cells. PROTAC 10 was synthesized by using modular click chemistry (CuAAC), strategically incorporating a central triazole ring flanked by flexible alkyl spacers. It exhibited potent antiviral activity (IC50 = 3.12 μM). Molecular dynamics simulations revealed that its engineered linker enhances cooperativity, ternary complex stability (ΔGTER = -247 kcal/mol), and chameleonic character. This study provides a strategic framework to design antiviral PROTACs through rational linker optimization that enables selective viral protein degradation.