To address the challenges of drilling fluid loss, reservoir contamination, difficulties in post-operation plug removal, and poor degradation controllability of temporary plugging agents in fractured reservoirs, a degradable temporary plugging agent ZDJ with a core–shell structure was developed. This agent was synthesized using natural waxy starch and polylactic acid ( PLA ) as the core materials via graft copolymerization to form starch-grafted PLA copolymer ( St-g-PLA ) , which was further encapsulated by a cross-linked polyacrylamide shell. This study systematically investigated the chemical structure, thermal stability, particle size distribution, degradation behavior, plugging capacity, and reservoir protection performance of ZDJ. The results demonstrated that ZDJ particles exhibited excellent thermal stability. The core–shell structure effectively delayed the degradation process, allowing the degradation period to be controlled within 5–20 d. Sand bed and wide-fracture plugging tests showed that ZDJ achieved pressure-bearing capacities of up to 8 MPa and 5 MPa in 3 mm and 5 mm fractures, respectively, indicating superior plugging performance. Core flow experiments revealed that the permeability recovery value after degradation exceeded 94%, with minimal reservoir damage. The ZDJ temporary plugging agent fulfilled the design objectives of "controllable plugging, complete degradation, and reservoir protection, .