Abstract: Metaiodobenzyl guanidine (MIBG) was labeled with ¹²³I using the catalyst of cuprous. The stability in vitro at atmospheric temperature and the biodistribution in normal mouse of ¹²³I-MIBG were studied. The labeling yield is over 95% at optimizing labeling conditions. The prepared ¹²³I-MIBG shows high stability after incubating at room temperature for over 48 h with different radioactive concentrations and specific activities. The highest uptake of ¹²³I-MIBG with (6.18±1.01) %ID•g^-1 is found in adrenals 1 h after injection according to the result of in vivo biodistribution in mouse. There are uptake in heart, lung, kidney and intestine, but the uptake in blood is low. The biodistribution and metabolism of ¹²³I-MIBG are accordance with reported results.