The widespread presence of antibiotic residues in animal-derived foods poses serious risks to public health and the environment, emphasizing the need for urgent action. This study presented a novel lightweight, popcorn-like magnetic molecularly imprinted polymer (LPR-MMIPs) with protein-resistant properties, for the selective enrichment of tetracycline (TC) antibiotics in milk. During the preparation of LPR-MMIPs, bovine serum albumin (BSA) was used as the functional monomer, and tris(2-carboxyethyl)phosphine (TCEP) served as the reducing agent. Using a "one-stone-two-birds" strategy, TCEP not only converted the α-helical structure of BSA to a β-folded conformation for imprinting on the Fe