Abstract: To investigate the preparation of radioiodinated MnTBAP and its biodistribution in mice, MnTBAP was labeled with ¹³¹I using the iodogen method. the radiolabeled compound was characterized by polymide TLC, in which the substratum of saline was used as developing agent. Biodistribution studies were carried out in KM mice. At different times after radiopharmaceutical i.v. administration (185 kBq ¹³¹I-MnTBAP/mouse, n=6), the animals were sacrificed. Blood samples and the tissues of interested were collected, weighted and counted. The percent injected does per gram (%ID/g) was calculated for each sample. The labeling yield of ¹³¹I-MnTBAP is 96.3% and its radiochemical purity(RCP) are 96%, 95% and 94.5% at 2, 24 and 48h, respectively. Biodistribution in mice demonstrates that ¹³¹I-MnTBAP is extensive, and it is metabolized mainly in liver and kidney, as indicated by their uptake of 8.34%ID/g and 12.23%ID/g at 5min, 0.34%ID/g and 0.73%ID/g at 4h, respectively. The results also show that ¹³¹I-MnTBAP could not penetrate the blood-brain barrier. The activity in thyroid increases with time. In conclusion, ¹³¹I-MnTBAP is stable and it is metabolized mainly in liver and kidney, worthy of further investigation to trace the compound in vivo and in vitro.