Abstract: The radiolabeling method of polypeptide (cNGQGEQc) for specific targeting lung cancer with ¹³¹I was established, and the biodistribution of ¹³¹I-cNGQGEQc in normal mice was carried out. Radiolabeling of polypeptide with ¹³¹I was performed by chloramines-T method by tyrosine linked its N-terminal. The labeling ratio and radiochemical purity were determined using paper chromatography. The octanol-water partition coefficient and stability in vitro in saline and normal human serum of labeling polypeptide were also determined. The biodistribution of ¹³¹I-cNGQGEQc in normal mice were measured through caudal vein injection of the labeled peptide. The results showed that the labeling yield of ¹³¹I-cNGQGEQc was more than 90% with specific activity of 0.4 TBq/g. The ¹³¹I-cNGQGEQc had good stability in saline and normal human serum. The octanol-water partition coefficient lgP=1.68, which indicate that radiolabeled polypeptide was water soluble. The biodistribution in mice demonstrated that the radioactivity in kidney was obviously higher than that of other organs, and it was metabolized mainly in kidney, as indicated by their uptake of (10.59±4.66)%ID/g at 1 h and (1.79±0. 89)%ID/g at 12 h, respectively. In conclusion, ¹³¹I-cNGQGEQc can be easily labeled with a high labeling ratio and was stable in vitro. It has good distribution characteristics, and can be used in further study on targeting diagnosis and treatment.