Glass fiber reinforced polymer composites (GFRPCs) based on thermoset polymer have been deployed in a variety of industrial sectors. However, a major drawback of thermoset polymeric composites is their significant contributions to waste and environmental pollution due to the challenges in recycling, reprocessing, and reutilization. Here, a sustainable thermosetting polyurethane vitrimer is developed by forming dynamic aromatic disulfide bonds. The obtained polyurethane vitrimer exhibits good mechanical properties and remarkable reprocessability. Under a large deformation or pulverizing, it can completely restore to its original mechanical properties of 30 MPa of strength and 407% elongation at break by 5-minute thermal reparation at 100 ℃. Moreover, the unique properties of the polyurethane vitrimer enables a novel technology for processing GFRPCs, namely “blocks-building” process, in which the fully cured single-layer prepregs could be effectively integrated into multiple layers.