Abstract: OxLDL-Ab was labeled with ¹²⁵I by the Iodogen method, and the labeling was purified by PD-10 column. The optimal condition of radiolabeling reaction was determined. The stability and affinity to OxLDL of ¹²⁵I-OxLDL-Ab in vitro were evaluated as well. The labeling yield of ¹²⁵I-OxLDL-Ab was more than 80% and the radiochemical purity was more than 95%. The results of in vitro stability studies showed that the radiochemical purity of ¹²⁵I-OxLDL-Ab declined less than 5% after 96 h storage under following condition: 0.9%NaCl, 2%BSA in 0.9%NaCl solution and human serum at 4 ℃ respectively. In the binding experiments of ¹²⁵I-OxLDL-Ab and OxLDL, Ka was (1.06±0.13)×1010 L/mol. The results showed that ¹²⁵I-OxLDL-Ab had high stability and high affinity to OxLDL, so it was worthy of further research for in vitro diagnosis kit.