Rubber exhibits excellent mechanical properties after cross-linking, which provides a strong foundation for its application across various fields. However, the intricate cross-linked network structure significantly impairs the reprocessing capabilities of rubber materials, thereby posing difficulties for their recycling. To overcome this challenge, we utilize a twin-screw extruder for the devulcanization-grafting modification of waste cross-linked ethylene propylene diene monomer (EPDM), facilitating large-scale recycling and processing of waste rubber while simultaneously maximizing the performance of reclaimed rubber. Under thermal shear, the desulfurizing agent zinc diethyl dithiocarbamate (ZDC) reacts with the cross-linking bonds (-S-S-, -C-S-) in waste rubber, leading to the scission of the cross-linked chains and the subsequent opening of the rubber's cross-linked network. Simultaneously, the graft modification with maleic anhydride (MAH) introduces new functional groups (-OH/-COOH), which can improve its processing performance. Compared with devulcanization modified waste rubber and graft modified waste rubber alone, devulcanization-grafting modified waste rubber exhibited better tensile modulus, tensile strength (12.02 MPa), and tear strength (29.91 kN/m). Furthermore, the tensile strength of recycled rubber was comparable to that of the original rubber. By adopting this technology, the challenges of environmental pollution and resource waste caused by the accumulation of waste rubber can be effectively addressed, providing a new solution for the sustainable utilization of waste rubber.